[V6,19/27] vfio-pci: cpr part 1 (fd and dma)

Commit Message

Steven Sistare Aug. 6, 2021, 9:43 p.m. UTC

Enable vfio-pci devices to be saved and restored across an exec restart
of qemu.

At vfio creation time, save the value of vfio container, group, and device
descriptors in cpr state.

In cpr-save and cpr-exec, suspend the use of virtual addresses in DMA
mappings with VFIO_DMA_UNMAP_FLAG_VADDR, because guest ram will be remapped
at a different VA after exec.  DMA to already-mapped pages continues.  Save
the msi message area as part of vfio-pci vmstate, save the interrupt and
notifier eventfd's in cpr state, and clear the close-on-exec flag for the
vfio descriptors.  The flag is not cleared earlier because the descriptors
should not persist across miscellaneous fork and exec calls that may be
performed during normal operation.

On qemu restart, vfio_realize() finds the descriptor env vars, uses
the descriptors, and notes that the device is being reused.  Device and
iommu state is already configured, so operations in vfio_realize that
would modify the configuration are skipped for a reused device, including
vfio ioctl's and writes to PCI configuration space.  The result is that
vfio_realize constructs qemu data structures that reflect the current
state of the device.  However, the reconstruction is not complete until
cpr-load is called. cpr-load loads the msi data and finds eventfds in cpr
state.  It rebuilds vector data structures and attaches the interrupts to
the new KVM instance.  cpr-load then walks the flattened ranges of the
vfio_address_spaces and calls VFIO_DMA_MAP_FLAG_VADDR to inform the kernel
of the new VA's.  Lastly, it starts the VM and suppresses vfio device reset.

This functionality is delivered by 3 patches for clarity.  Part 1 handles
device file descriptors and DMA.  Part 2 adds eventfd and MSI/MSI-X vector
support.  Part 3 adds INTX support.

Signed-off-by: Steve Sistare <[e-mail]>
---
 MAINTAINERS                   |   1 +
 hw/pci/pci.c                  |   4 ++
 hw/vfio/common.c              |  69 ++++++++++++++++--
 hw/vfio/cpr.c                 | 160 ++++++++++++++++++++++++++++++++++++++++++
 hw/vfio/meson.build           |   1 +
 hw/vfio/pci.c                 |  57 +++++++++++++++
 hw/vfio/trace-events          |   1 +
 include/hw/pci/pci.h          |   1 +
 include/hw/vfio/vfio-common.h |   5 ++
 include/migration/cpr.h       |   3 +
 linux-headers/linux/vfio.h    |   6 ++
 migration/cpr.c               |  10 ++-
 migration/target.c            |  14 ++++
 13 files changed, 325 insertions(+), 7 deletions(-)
 create mode 100644 hw/vfio/cpr.c

Comments

Alex Williamson Aug. 10, 2021, 5:06 p.m. UTC | #1

On Fri,  6 Aug 2021 14:43:53 -0700
Steve Sistare <[e-mail]> wrote:

> Enable vfio-pci devices to be saved and restored across an exec restart
> of qemu.
> 
> At vfio creation time, save the value of vfio container, group, and device
> descriptors in cpr state.
> 
> In cpr-save and cpr-exec, suspend the use of virtual addresses in DMA
> mappings with VFIO_DMA_UNMAP_FLAG_VADDR, because guest ram will be remapped
> at a different VA after exec.  DMA to already-mapped pages continues.  Save
> the msi message area as part of vfio-pci vmstate, save the interrupt and
> notifier eventfd's in cpr state, and clear the close-on-exec flag for the
> vfio descriptors.  The flag is not cleared earlier because the descriptors
> should not persist across miscellaneous fork and exec calls that may be
> performed during normal operation.
> 
> On qemu restart, vfio_realize() finds the descriptor env vars, uses
> the descriptors, and notes that the device is being reused.  Device and
> iommu state is already configured, so operations in vfio_realize that
> would modify the configuration are skipped for a reused device, including
> vfio ioctl's and writes to PCI configuration space.  The result is that
> vfio_realize constructs qemu data structures that reflect the current
> state of the device.  However, the reconstruction is not complete until
> cpr-load is called. cpr-load loads the msi data and finds eventfds in cpr
> state.  It rebuilds vector data structures and attaches the interrupts to
> the new KVM instance.  cpr-load then walks the flattened ranges of the
> vfio_address_spaces and calls VFIO_DMA_MAP_FLAG_VADDR to inform the kernel
> of the new VA's.  Lastly, it starts the VM and suppresses vfio device reset.
> 
> This functionality is delivered by 3 patches for clarity.  Part 1 handles
> device file descriptors and DMA.  Part 2 adds eventfd and MSI/MSI-X vector
> support.  Part 3 adds INTX support.
> 
> Signed-off-by: Steve Sistare <[e-mail]>
> ---
>  MAINTAINERS                   |   1 +
>  hw/pci/pci.c                  |   4 ++
>  hw/vfio/common.c              |  69 ++++++++++++++++--
>  hw/vfio/cpr.c                 | 160 ++++++++++++++++++++++++++++++++++++++++++
>  hw/vfio/meson.build           |   1 +
>  hw/vfio/pci.c                 |  57 +++++++++++++++
>  hw/vfio/trace-events          |   1 +
>  include/hw/pci/pci.h          |   1 +
>  include/hw/vfio/vfio-common.h |   5 ++
>  include/migration/cpr.h       |   3 +
>  linux-headers/linux/vfio.h    |   6 ++
>  migration/cpr.c               |  10 ++-
>  migration/target.c            |  14 ++++
>  13 files changed, 325 insertions(+), 7 deletions(-)
>  create mode 100644 hw/vfio/cpr.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a9d2ed8..3132965 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -2904,6 +2904,7 @@ CPR
>  M: Steve Sistare <[e-mail]>
>  M: Mark Kanda <[e-mail]>
>  S: Maintained
> +F: hw/vfio/cpr.c
>  F: include/migration/cpr.h
>  F: migration/cpr.c
>  F: qapi/cpr.json
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index 59408a3..b9c6ca1 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -307,6 +307,10 @@ static void pci_do_device_reset(PCIDevice *dev)
>  {
>      int r;
>  
> +    if (dev->reused) {
> +        return;
> +    }
> +
>      pci_device_deassert_intx(dev);
>      assert(dev->irq_state == 0);
>  
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 7918c0d..872a1ac 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -31,6 +31,7 @@
>  #include "exec/memory.h"
>  #include "exec/ram_addr.h"
>  #include "hw/hw.h"
> +#include "migration/cpr.h"
>  #include "qemu/error-report.h"
>  #include "qemu/main-loop.h"
>  #include "qemu/range.h"
> @@ -464,6 +465,10 @@ static int vfio_dma_unmap(VFIOContainer *container,
>          return vfio_dma_unmap_bitmap(container, iova, size, iotlb);
>      }
>  
> +    if (container->reused) {
> +        return 0;
> +    }
> +
>      while (ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, &unmap)) {
>          /*
>           * The type1 backend has an off-by-one bug in the kernel (71a7d3d78e3c
> @@ -501,6 +506,10 @@ static int vfio_dma_map(VFIOContainer *container, hwaddr iova,
>          .size = size,
>      };
>  
> +    if (container->reused) {
> +        return 0;
> +    }
> +
>      if (!readonly) {
>          map.flags |= VFIO_DMA_MAP_FLAG_WRITE;
>      }
> @@ -1872,6 +1881,10 @@ static int vfio_init_container(VFIOContainer *container, int group_fd,
>      if (iommu_type < 0) {
>          return iommu_type;
>      }
> +    if (container->reused) {
> +        container->iommu_type = iommu_type;
> +        return 0;
> +    }
>  

I'd like to see more comments throughout, but particularly where we're
dumping out of functions for reused containers, groups, and devices.
For instance map/unmap we're assuming we'll reach the same IOMMU
mapping state we had previously, how do we validate that, why can't we
only set vaddr in the mapping path rather than skipping it for a later
pass at the flatmap, do we actually see unmaps, is deferring listener
registration an alternate option, which specific reset path are we
trying to defer, why are VFIOPCIDevices the only PCIDevices that set
reused, there are some assumptions about the iommu_type that could use
further description, etc.

>      ret = ioctl(group_fd, VFIO_GROUP_SET_CONTAINER, &container->fd);
>      if (ret) {
> @@ -1972,6 +1985,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>  {
>      VFIOContainer *container;
>      int ret, fd;
> +    bool reused;
>      VFIOAddressSpace *space;
>  
>      space = vfio_get_address_space(as);
> @@ -2007,7 +2021,13 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>       * details once we know which type of IOMMU we are using.
>       */
>  
> +    fd = cpr_find_fd("vfio_container_for_group", group->groupid);
> +    reused = (fd >= 0);
> +
>      QLIST_FOREACH(container, &space->containers, next) {
> +        if (container->fd == fd) {
> +            break;
> +        }
>          if (!ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &container->fd)) {


Letting the reused case call this ioctl feels a little sloppy.  I'm
assuming we've tested this in a vIOMMU config or other setups where
we'd actually have multiple containers and we're relying on the ioctl
failing, but why call it at all if we already know the group is
attached to a container.


>              ret = vfio_ram_block_discard_disable(container, true);
>              if (ret) {
> @@ -2020,14 +2040,25 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>                  }
>                  return ret;
>              }
> -            group->container = container;
> -            QLIST_INSERT_HEAD(&container->group_list, group, container_next);
> +            break;
> +        }
> +    }
> +
> +    if (container) {
> +        group->container = container;
> +        QLIST_INSERT_HEAD(&container->group_list, group, container_next);
> +        if (!reused) {
>              vfio_kvm_device_add_group(group);
> -            return 0;
> +            cpr_save_fd("vfio_container_for_group", group->groupid,
> +                        container->fd);
>          }
> +        return 0;
> +    }
> +
> +    if (!reused) {
> +        fd = qemu_open_old("/dev/vfio/vfio", O_RDWR);
>      }
>  
> -    fd = qemu_open_old("/dev/vfio/vfio", O_RDWR);
>      if (fd < 0) {
>          error_setg_errno(errp, errno, "failed to open /dev/vfio/vfio");
>          ret = -errno;
> @@ -2045,6 +2076,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>      container = g_malloc0(sizeof(*container));
>      container->space = space;
>      container->fd = fd;
> +    container->reused = reused;
>      container->error = NULL;
>      container->dirty_pages_supported = false;
>      container->dma_max_mappings = 0;
> @@ -2183,6 +2215,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>      }
>  
>      container->initialized = true;
> +    cpr_save_fd("vfio_container_for_group", group->groupid, fd);
>  
>      return 0;
>  listener_release_exit:
> @@ -2212,6 +2245,7 @@ static void vfio_disconnect_container(VFIOGroup *group)
>  
>      QLIST_REMOVE(group, container_next);
>      group->container = NULL;
> +    cpr_delete_fd("vfio_container_for_group", group->groupid);
>  
>      /*
>       * Explicitly release the listener first before unset container,
> @@ -2253,6 +2287,7 @@ VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp)
>      VFIOGroup *group;
>      char path[32];
>      struct vfio_group_status status = { .argsz = sizeof(status) };
> +    bool reused;
>  
>      QLIST_FOREACH(group, &vfio_group_list, next) {
>          if (group->groupid == groupid) {
> @@ -2270,7 +2305,13 @@ VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp)
>      group = g_malloc0(sizeof(*group));
>  
>      snprintf(path, sizeof(path), "/dev/vfio/%d", groupid);
> -    group->fd = qemu_open_old(path, O_RDWR);
> +
> +    group->fd = cpr_find_fd("vfio_group", groupid);
> +    reused = (group->fd >= 0);
> +    if (!reused) {
> +        group->fd = qemu_open_old(path, O_RDWR);
> +    }
> +
>      if (group->fd < 0) {
>          error_setg_errno(errp, errno, "failed to open %s", path);
>          goto free_group_exit;
> @@ -2304,6 +2345,10 @@ VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp)
>  
>      QLIST_INSERT_HEAD(&vfio_group_list, group, next);
>  
> +    if (!reused) {
> +        cpr_save_fd("vfio_group", groupid, group->fd);
> +    }
> +
>      return group;
>  
>  close_fd_exit:
> @@ -2328,6 +2373,7 @@ void vfio_put_group(VFIOGroup *group)
>      vfio_disconnect_container(group);
>      QLIST_REMOVE(group, next);
>      trace_vfio_put_group(group->fd);
> +    cpr_delete_fd("vfio_group", group->groupid);
>      close(group->fd);
>      g_free(group);
>  
> @@ -2341,8 +2387,14 @@ int vfio_get_device(VFIOGroup *group, const char *name,
>  {
>      struct vfio_device_info dev_info = { .argsz = sizeof(dev_info) };
>      int ret, fd;
> +    bool reused;
> +
> +    fd = cpr_find_fd(name, 0);
> +    reused = (fd >= 0);
> +    if (!reused) {
> +        fd = ioctl(group->fd, VFIO_GROUP_GET_DEVICE_FD, name);
> +    }
>  
> -    fd = ioctl(group->fd, VFIO_GROUP_GET_DEVICE_FD, name);
>      if (fd < 0) {
>          error_setg_errno(errp, errno, "error getting device from group %d",
>                           group->groupid);
> @@ -2387,6 +2439,10 @@ int vfio_get_device(VFIOGroup *group, const char *name,
>      vbasedev->num_irqs = dev_info.num_irqs;
>      vbasedev->num_regions = dev_info.num_regions;
>      vbasedev->flags = dev_info.flags;
> +    vbasedev->reused = reused;
> +    if (!reused) {
> +        cpr_save_fd(name, 0, fd);
> +    }
>  
>      trace_vfio_get_device(name, dev_info.flags, dev_info.num_regions,
>                            dev_info.num_irqs);
> @@ -2403,6 +2459,7 @@ void vfio_put_base_device(VFIODevice *vbasedev)
>      QLIST_REMOVE(vbasedev, next);
>      vbasedev->group = NULL;
>      trace_vfio_put_base_device(vbasedev->fd);
> +    cpr_delete_fd(vbasedev->name, 0);
>      close(vbasedev->fd);
>  }
>  
> diff --git a/hw/vfio/cpr.c b/hw/vfio/cpr.c
> new file mode 100644
> index 0000000..0981d31
> --- /dev/null
> +++ b/hw/vfio/cpr.c
> @@ -0,0 +1,160 @@
> +/*
> + * Copyright (c) 2021 Oracle and/or its affiliates.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include <sys/ioctl.h>
> +#include <linux/vfio.h>
> +#include "hw/vfio/vfio-common.h"
> +#include "sysemu/kvm.h"
> +#include "qapi/error.h"
> +#include "trace.h"
> +
> +static int
> +vfio_dma_unmap_vaddr_all(VFIOContainer *container, Error **errp)
> +{
> +    struct vfio_iommu_type1_dma_unmap unmap = {
> +        .argsz = sizeof(unmap),
> +        .flags = VFIO_DMA_UNMAP_FLAG_VADDR | VFIO_DMA_UNMAP_FLAG_ALL,
> +        .iova = 0,
> +        .size = 0,
> +    };
> +    if (ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, &unmap)) {
> +        error_setg_errno(errp, errno, "vfio_dma_unmap_vaddr_all");
> +        return -errno;
> +    }
> +    return 0;
> +}
> +
> +static int vfio_dma_map_vaddr(VFIOContainer *container, hwaddr iova,
> +                              ram_addr_t size, void *vaddr,
> +                              Error **errp)
> +{
> +    struct vfio_iommu_type1_dma_map map = {
> +        .argsz = sizeof(map),
> +        .flags = VFIO_DMA_MAP_FLAG_VADDR,
> +        .vaddr = (__u64)(uintptr_t)vaddr,
> +        .iova = iova,
> +        .size = size,
> +    };
> +    if (ioctl(container->fd, VFIO_IOMMU_MAP_DMA, &map)) {
> +        error_setg_errno(errp, errno,
> +                         "vfio_dma_map_vaddr(iova %lu, size %ld, va %p)",
> +                         iova, size, vaddr);
> +        return -errno;
> +    }
> +    return 0;
> +}
> +
> +static int
> +vfio_region_remap(MemoryRegionSection *section, void *handle, Error **errp)
> +{
> +    MemoryRegion *mr = section->mr;
> +    VFIOContainer *container = handle;
> +    const char *name = memory_region_name(mr);
> +    ram_addr_t size = int128_get64(section->size);
> +    hwaddr offset, iova, roundup;
> +    void *vaddr;
> +
> +    if (vfio_listener_skipped_section(section) || memory_region_is_iommu(mr)) {

A comment reminding us why we're also skipping iommu regions would be
useful.  It's not clear to me why this needs to happen separately from
the listener.  There's a sufficient degree of magic here that I'm
afraid it's going to get broken too easily if it's left to me trying to
remember how it's supposed to work.

> +        return 0;
> +    }
> +
> +    offset = section->offset_within_address_space;
> +    iova = REAL_HOST_PAGE_ALIGN(offset);
> +    roundup = iova - offset;
> +    size -= roundup;
> +    size = REAL_HOST_PAGE_ALIGN(size);
> +    vaddr = memory_region_get_ram_ptr(mr) +
> +            section->offset_within_region + roundup;
> +
> +    trace_vfio_region_remap(name, container->fd, iova, iova + size - 1, vaddr);
> +    return vfio_dma_map_vaddr(container, iova, size, vaddr, errp);
> +}
> +
> +bool vfio_is_cpr_capable(VFIOContainer *container, Error **errp)
> +{
> +    if (!ioctl(container->fd, VFIO_CHECK_EXTENSION, VFIO_UPDATE_VADDR) ||
> +        !ioctl(container->fd, VFIO_CHECK_EXTENSION, VFIO_UNMAP_ALL)) {
> +        error_setg(errp, "VFIO container does not support VFIO_UPDATE_VADDR "
> +                         "or VFIO_UNMAP_ALL");
> +        return false;
> +    } else {
> +        return true;
> +    }
> +}
> +
> +int vfio_cpr_save(Error **errp)
> +{
> +    ERRP_GUARD();
> +    VFIOAddressSpace *space, *last_space;
> +    VFIOContainer *container, *last_container;
> +
> +    QLIST_FOREACH(space, &vfio_address_spaces, list) {
> +        QLIST_FOREACH(container, &space->containers, next) {
> +            if (!vfio_is_cpr_capable(container, errp)) {
> +                return -1;
> +            }
> +        }
> +    }
> +
> +    QLIST_FOREACH(space, &vfio_address_spaces, list) {
> +        QLIST_FOREACH(container, &space->containers, next) {
> +            if (vfio_dma_unmap_vaddr_all(container, errp)) {
> +                goto unwind;
> +            }
> +        }
> +    }
> +    return 0;
> +
> +unwind:
> +    last_space = space;
> +    last_container = container;
> +    QLIST_FOREACH(space, &vfio_address_spaces, list) {
> +        QLIST_FOREACH(container, &space->containers, next) {
> +            Error *err;
> +
> +            if (space == last_space && container == last_container) {
> +                break;
> +            }

Isn't it sufficient to only test the container?  I think we'd be in
trouble if we found a container on multiple address space lists.  Too
bad we don't have a continue_reverse foreach or it might be trivial to
convert to a qtailq. 

> +            if (address_space_flat_for_each_section(space->as,
> +                                                    vfio_region_remap,
> +                                                    container, &err)) {
> +                error_prepend(errp, "%s", error_get_pretty(err));
> +                error_free(err);
> +            }
> +        }
> +    }
> +    return -1;
> +}
> +
> +int vfio_cpr_load(Error **errp)
> +{
> +    VFIOAddressSpace *space;
> +    VFIOContainer *container;
> +    VFIOGroup *group;
> +    VFIODevice *vbasedev;
> +
> +    QLIST_FOREACH(space, &vfio_address_spaces, list) {
> +        QLIST_FOREACH(container, &space->containers, next) {
> +            if (!vfio_is_cpr_capable(container, errp)) {
> +                return -1;
> +            }
> +            container->reused = false;
> +            if (address_space_flat_for_each_section(space->as,
> +                                                    vfio_region_remap,
> +                                                    container, errp)) {
> +                return -1;
> +            }
> +        }
> +    }
> +    QLIST_FOREACH(group, &vfio_group_list, next) {
> +        QLIST_FOREACH(vbasedev, &group->device_list, next) {
> +            vbasedev->reused = false;
> +        }
> +    }

The above is a bit disjoint between group/device and space/container,
how about walking container->group_list rather than the global group
list?

> +    return 0;
> +}
> diff --git a/hw/vfio/meson.build b/hw/vfio/meson.build
> index da9af29..e247b2b 100644
> --- a/hw/vfio/meson.build
> +++ b/hw/vfio/meson.build
> @@ -5,6 +5,7 @@ vfio_ss.add(files(
>    'migration.c',
>  ))
>  vfio_ss.add(when: 'CONFIG_VFIO_PCI', if_true: files(
> +  'cpr.c',
>    'display.c',
>    'pci-quirks.c',
>    'pci.c',
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index e8e371e..64e2557 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -29,6 +29,7 @@
>  #include "hw/qdev-properties.h"
>  #include "hw/qdev-properties-system.h"
>  #include "migration/vmstate.h"
> +#include "migration/cpr.h"
>  #include "qemu/error-report.h"
>  #include "qemu/main-loop.h"
>  #include "qemu/module.h"
> @@ -2899,6 +2900,7 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
>          vfio_put_group(group);
>          goto error;
>      }
> +    pdev->reused = vdev->vbasedev.reused;
>  
>      vfio_populate_device(vdev, &err);
>      if (err) {
> @@ -3168,6 +3170,10 @@ static void vfio_pci_reset(DeviceState *dev)
>  {
>      VFIOPCIDevice *vdev = VFIO_PCI(dev);
>  
> +    if (vdev->pdev.reused) {
> +        return;
> +    }

Why are we the only ones using PCIDevice.reused and why are we testing
that rather than VFIOPCIDevice.reused above?  These have different
lifecycles and the difference is too subtle, esp. w/o comments.

> +
>      trace_vfio_pci_reset(vdev->vbasedev.name);
>  
>      vfio_pci_pre_reset(vdev);
> @@ -3275,6 +3281,56 @@ static Property vfio_pci_dev_properties[] = {
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> +static void vfio_merge_config(VFIOPCIDevice *vdev)
> +{
> +    PCIDevice *pdev = &vdev->pdev;
> +    int size = MIN(pci_config_size(pdev), vdev->config_size);
> +    g_autofree uint8_t *phys_config = g_malloc(size);
> +    uint32_t mask;
> +    int ret, i;
> +
> +    ret = pread(vdev->vbasedev.fd, phys_config, size, vdev->config_offset);
> +    if (ret < size) {
> +        ret = ret < 0 ? errno : EFAULT;
> +        error_report("failed to read device config space: %s", strerror(ret));
> +        return;
> +    }
> +
> +    for (i = 0; i < size; i++) {
> +        mask = vdev->emulated_config_bits[i];
> +        pdev->config[i] = (pdev->config[i] & mask) | (phys_config[i] & ~mask);
> +    }
> +}
> +
> +static int vfio_pci_post_load(void *opaque, int version_id)
> +{
> +    VFIOPCIDevice *vdev = opaque;
> +    PCIDevice *pdev = &vdev->pdev;
> +
> +    vfio_merge_config(vdev);
> +
> +    pdev->reused = false;
> +
> +    return 0;
> +}
> +
> +static bool vfio_pci_needed(void *opaque)
> +{
> +    return cpr_mode() == CPR_MODE_RESTART;
> +}
> +
> +static const VMStateDescription vfio_pci_vmstate = {
> +    .name = "vfio-pci",
> +    .unmigratable = 1,


Doesn't this break the experimental (for now) migration support?


> +    .version_id = 0,
> +    .minimum_version_id = 0,
> +    .post_load = vfio_pci_post_load,
> +    .needed = vfio_pci_needed,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>  static void vfio_pci_dev_class_init(ObjectClass *klass, void *data)
>  {
>      DeviceClass *dc = DEVICE_CLASS(klass);
> @@ -3282,6 +3338,7 @@ static void vfio_pci_dev_class_init(ObjectClass *klass, void *data)
>  
>      dc->reset = vfio_pci_reset;
>      device_class_set_props(dc, vfio_pci_dev_properties);
> +    dc->vmsd = &vfio_pci_vmstate;
>      dc->desc = "VFIO-based PCI device assignment";
>      set_bit(DEVICE_CATEGORY_MISC, dc->categories);
>      pdc->realize = vfio_realize;
> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
> index 0ef1b5f..63dd0fe 100644
> --- a/hw/vfio/trace-events
> +++ b/hw/vfio/trace-events
> @@ -118,6 +118,7 @@ vfio_region_sparse_mmap_header(const char *name, int index, int nr_areas) "Devic
>  vfio_region_sparse_mmap_entry(int i, unsigned long start, unsigned long end) "sparse entry %d [0x%lx - 0x%lx]"
>  vfio_get_dev_region(const char *name, int index, uint32_t type, uint32_t subtype) "%s index %d, %08x/%0x8"
>  vfio_dma_unmap_overflow_workaround(void) ""
> +vfio_region_remap(const char *name, int fd, uint64_t iova_start, uint64_t iova_end, void *vaddr) "%s fd %d 0x%"PRIx64" - 0x%"PRIx64" [%p]"
>  
>  # platform.c
>  vfio_platform_base_device_init(char *name, int groupid) "%s belongs to group #%d"
> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> index bf5be06..f079423 100644
> --- a/include/hw/pci/pci.h
> +++ b/include/hw/pci/pci.h
> @@ -360,6 +360,7 @@ struct PCIDevice {
>      /* ID of standby device in net_failover pair */
>      char *failover_pair_id;
>      uint32_t acpi_index;
> +    bool reused;
>  };
>  
>  void pci_register_bar(PCIDevice *pci_dev, int region_num,
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index cb04cc6..0766cc4 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -85,6 +85,7 @@ typedef struct VFIOContainer {
>      Error *error;
>      bool initialized;
>      bool dirty_pages_supported;
> +    bool reused;
>      uint64_t dirty_pgsizes;
>      uint64_t max_dirty_bitmap_size;
>      unsigned long pgsizes;
> @@ -136,6 +137,7 @@ typedef struct VFIODevice {
>      bool no_mmap;
>      bool ram_block_discard_allowed;
>      bool enable_migration;
> +    bool reused;
>      VFIODeviceOps *ops;
>      unsigned int num_irqs;
>      unsigned int num_regions;
> @@ -212,6 +214,9 @@ VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp);
>  void vfio_put_group(VFIOGroup *group);
>  int vfio_get_device(VFIOGroup *group, const char *name,
>                      VFIODevice *vbasedev, Error **errp);
> +int vfio_cpr_save(Error **errp);
> +int vfio_cpr_load(Error **errp);
> +bool vfio_is_cpr_capable(VFIOContainer *container, Error **errp);
>  
>  extern const MemoryRegionOps vfio_region_ops;
>  typedef QLIST_HEAD(VFIOGroupList, VFIOGroup) VFIOGroupList;
> diff --git a/include/migration/cpr.h b/include/migration/cpr.h
> index 83f69c9..e9b987f 100644
> --- a/include/migration/cpr.h
> +++ b/include/migration/cpr.h
> @@ -25,4 +25,7 @@ int cpr_state_load(Error **errp);
>  CprMode cpr_state_mode(void);
>  void cpr_state_print(void);
>  
> +int cpr_vfio_save(Error **errp);
> +int cpr_vfio_load(Error **errp);
> +
>  #endif
> diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h
> index e680594..48a02c0 100644
> --- a/linux-headers/linux/vfio.h
> +++ b/linux-headers/linux/vfio.h
> @@ -52,6 +52,12 @@
>  /* Supports the vaddr flag for DMA map and unmap */
>  #define VFIO_UPDATE_VADDR		10
           ^^^^^^^^^^^^^^^^^

It's already there.  Thanks,

Alex

>  
> +/* Supports VFIO_DMA_UNMAP_FLAG_ALL */
> +#define VFIO_UNMAP_ALL                        9
> +
> +/* Supports VFIO DMA map and unmap with the VADDR flag */
> +#define VFIO_UPDATE_VADDR              10
> +
>  /*
>   * The IOCTL interface is designed for extensibility by embedding the
>   * structure length (argsz) and flags into structures passed between
> diff --git a/migration/cpr.c b/migration/cpr.c
> index 72a5f4b..16f11bd 100644
> --- a/migration/cpr.c
> +++ b/migration/cpr.c
> @@ -7,6 +7,7 @@
>  
>  #include "qemu/osdep.h"
>  #include "exec/memory.h"
> +#include "hw/vfio/vfio-common.h"
>  #include "io/channel-buffer.h"
>  #include "io/channel-file.h"
>  #include "migration.h"
> @@ -108,7 +109,9 @@ void qmp_cpr_exec(strList *args, Error **errp)
>          error_setg(errp, "cpr-exec requires cpr-save with restart mode");
>          return;
>      }
> -
> +    if (cpr_vfio_save(errp)) {
> +        return;
> +    }
>      cpr_walk_fd(preserve_fd, 0);
>      if (cpr_state_save(errp)) {
>          return;
> @@ -148,6 +151,11 @@ void qmp_cpr_load(const char *filename, Error **errp)
>          goto out;
>      }
>  
> +    if (cpr_active_mode == CPR_MODE_RESTART &&
> +        cpr_vfio_load(errp)) {
> +        goto out;
> +    }
> +
>      state = global_state_get_runstate();
>      if (state == RUN_STATE_RUNNING) {
>          vm_start();
> diff --git a/migration/target.c b/migration/target.c
> index 4390bf0..984bc9e 100644
> --- a/migration/target.c
> +++ b/migration/target.c
> @@ -8,6 +8,7 @@
>  #include "qemu/osdep.h"
>  #include "qapi/qapi-types-migration.h"
>  #include "migration.h"
> +#include "migration/cpr.h"
>  #include CONFIG_DEVICES
>  
>  #ifdef CONFIG_VFIO
> @@ -22,8 +23,21 @@ void populate_vfio_info(MigrationInfo *info)
>          info->vfio->transferred = vfio_mig_bytes_transferred();
>      }
>  }
> +
> +int cpr_vfio_save(Error **errp)
> +{
> +    return vfio_cpr_save(errp);
> +}
> +
> +int cpr_vfio_load(Error **errp)
> +{
> +    return vfio_cpr_load(errp);
> +}
> +
>  #else
>  
>  void populate_vfio_info(MigrationInfo *info) {}
> +int cpr_vfio_save(Error **errp) { return 0; }
> +int cpr_vfio_load(Error **errp) { return 0; }
>  
>  #endif /* CONFIG_VFIO */

Steven Sistare Aug. 23, 2021, 7:43 p.m. UTC | #2

On 8/10/2021 1:06 PM, Alex Williamson wrote:
> On Fri,  6 Aug 2021 14:43:53 -0700
> Steve Sistare <[e-mail]> wrote:
> 
>> Enable vfio-pci devices to be saved and restored across an exec restart
>> of qemu.
>>
>> At vfio creation time, save the value of vfio container, group, and device
>> descriptors in cpr state.
>>
>> In cpr-save and cpr-exec, suspend the use of virtual addresses in DMA
>> mappings with VFIO_DMA_UNMAP_FLAG_VADDR, because guest ram will be remapped
>> at a different VA after exec.  DMA to already-mapped pages continues.  Save
>> the msi message area as part of vfio-pci vmstate, save the interrupt and
>> notifier eventfd's in cpr state, and clear the close-on-exec flag for the
>> vfio descriptors.  The flag is not cleared earlier because the descriptors
>> should not persist across miscellaneous fork and exec calls that may be
>> performed during normal operation.
>>
>> On qemu restart, vfio_realize() finds the descriptor env vars, uses
>> the descriptors, and notes that the device is being reused.  Device and
>> iommu state is already configured, so operations in vfio_realize that
>> would modify the configuration are skipped for a reused device, including
>> vfio ioctl's and writes to PCI configuration space.  The result is that
>> vfio_realize constructs qemu data structures that reflect the current
>> state of the device.  However, the reconstruction is not complete until
>> cpr-load is called. cpr-load loads the msi data and finds eventfds in cpr
>> state.  It rebuilds vector data structures and attaches the interrupts to
>> the new KVM instance.  cpr-load then walks the flattened ranges of the
>> vfio_address_spaces and calls VFIO_DMA_MAP_FLAG_VADDR to inform the kernel
>> of the new VA's.  Lastly, it starts the VM and suppresses vfio device reset.
>>
>> This functionality is delivered by 3 patches for clarity.  Part 1 handles
>> device file descriptors and DMA.  Part 2 adds eventfd and MSI/MSI-X vector
>> support.  Part 3 adds INTX support.
>>
>> Signed-off-by: Steve Sistare <[e-mail]>
>> ---
>>  MAINTAINERS                   |   1 +
>>  hw/pci/pci.c                  |   4 ++
>>  hw/vfio/common.c              |  69 ++++++++++++++++--
>>  hw/vfio/cpr.c                 | 160 ++++++++++++++++++++++++++++++++++++++++++
>>  hw/vfio/meson.build           |   1 +
>>  hw/vfio/pci.c                 |  57 +++++++++++++++
>>  hw/vfio/trace-events          |   1 +
>>  include/hw/pci/pci.h          |   1 +
>>  include/hw/vfio/vfio-common.h |   5 ++
>>  include/migration/cpr.h       |   3 +
>>  linux-headers/linux/vfio.h    |   6 ++
>>  migration/cpr.c               |  10 ++-
>>  migration/target.c            |  14 ++++
>>  13 files changed, 325 insertions(+), 7 deletions(-)
>>  create mode 100644 hw/vfio/cpr.c
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index a9d2ed8..3132965 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -2904,6 +2904,7 @@ CPR
>>  M: Steve Sistare <[e-mail]>
>>  M: Mark Kanda <[e-mail]>
>>  S: Maintained
>> +F: hw/vfio/cpr.c
>>  F: include/migration/cpr.h
>>  F: migration/cpr.c
>>  F: qapi/cpr.json
>> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
>> index 59408a3..b9c6ca1 100644
>> --- a/hw/pci/pci.c
>> +++ b/hw/pci/pci.c
>> @@ -307,6 +307,10 @@ static void pci_do_device_reset(PCIDevice *dev)
>>  {
>>      int r;
>>  
>> +    if (dev->reused) {
>> +        return;
>> +    }
>> +
>>      pci_device_deassert_intx(dev);
>>      assert(dev->irq_state == 0);
>>  
>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
>> index 7918c0d..872a1ac 100644
>> --- a/hw/vfio/common.c
>> +++ b/hw/vfio/common.c
>> @@ -31,6 +31,7 @@
>>  #include "exec/memory.h"
>>  #include "exec/ram_addr.h"
>>  #include "hw/hw.h"
>> +#include "migration/cpr.h"
>>  #include "qemu/error-report.h"
>>  #include "qemu/main-loop.h"
>>  #include "qemu/range.h"
>> @@ -464,6 +465,10 @@ static int vfio_dma_unmap(VFIOContainer *container,
>>          return vfio_dma_unmap_bitmap(container, iova, size, iotlb);
>>      }
>>  
>> +    if (container->reused) {
>> +        return 0;
>> +    }
>> +
>>      while (ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, &unmap)) {
>>          /*
>>           * The type1 backend has an off-by-one bug in the kernel (71a7d3d78e3c
>> @@ -501,6 +506,10 @@ static int vfio_dma_map(VFIOContainer *container, hwaddr iova,
>>          .size = size,
>>      };
>>  
>> +    if (container->reused) {
>> +        return 0;
>> +    }
>> +
>>      if (!readonly) {
>>          map.flags |= VFIO_DMA_MAP_FLAG_WRITE;
>>      }
>> @@ -1872,6 +1881,10 @@ static int vfio_init_container(VFIOContainer *container, int group_fd,
>>      if (iommu_type < 0) {
>>          return iommu_type;
>>      }
>> +    if (container->reused) {
>> +        container->iommu_type = iommu_type;
>> +        return 0;
>> +    }
>>  
> 
> I'd like to see more comments throughout, but particularly where we're
> dumping out of functions for reused containers, groups, and devices.
> For instance map/unmap we're assuming we'll reach the same IOMMU
> mapping state we had previously, how do we validate that, why can't we
> only set vaddr in the mapping path rather than skipping it for a later
> pass at the flatmap, do we actually see unmaps, is deferring listener
> registration an alternate option, which specific reset path are we
> trying to defer, why are VFIOPCIDevices the only PCIDevices that set
> reused, there are some assumptions about the iommu_type that could use
> further description, etc.

Will do.

>>      ret = ioctl(group_fd, VFIO_GROUP_SET_CONTAINER, &container->fd);
>>      if (ret) {
>> @@ -1972,6 +1985,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>>  {
>>      VFIOContainer *container;
>>      int ret, fd;
>> +    bool reused;
>>      VFIOAddressSpace *space;
>>  
>>      space = vfio_get_address_space(as);
>> @@ -2007,7 +2021,13 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>>       * details once we know which type of IOMMU we are using.
>>       */
>>  
>> +    fd = cpr_find_fd("vfio_container_for_group", group->groupid);
>> +    reused = (fd >= 0);
>> +
>>      QLIST_FOREACH(container, &space->containers, next) {
>> +        if (container->fd == fd) {
>> +            break;
>> +        }
>>          if (!ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &container->fd)) {
> 
> Letting the reused case call this ioctl feels a little sloppy.  I'm
> assuming we've tested this in a vIOMMU config or other setups where
> we'd actually have multiple containers and we're relying on the ioctl
> failing, but why call it at all if we already know the group is
> attached to a container.

Good find, this was unintentional.  Will fix.

>>[...]
>> +++ b/hw/vfio/cpr.c
>> @@ -0,0 +1,160 @@
>> +/*
>> + * Copyright (c) 2021 Oracle and/or its affiliates.
>> + *
>> + * This work is licensed under the terms of the GNU GPL, version 2.
>> + * See the COPYING file in the top-level directory.
>> + */
>> +
>> +#include "qemu/osdep.h"
>> +#include <sys/ioctl.h>
>> +#include <linux/vfio.h>
>> +#include "hw/vfio/vfio-common.h"
>> +#include "sysemu/kvm.h"
>> +#include "qapi/error.h"
>> +#include "trace.h"
>> +
>> +static int
>> +vfio_dma_unmap_vaddr_all(VFIOContainer *container, Error **errp)
>> +{
>> +    struct vfio_iommu_type1_dma_unmap unmap = {
>> +        .argsz = sizeof(unmap),
>> +        .flags = VFIO_DMA_UNMAP_FLAG_VADDR | VFIO_DMA_UNMAP_FLAG_ALL,
>> +        .iova = 0,
>> +        .size = 0,
>> +    };
>> +    if (ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, &unmap)) {
>> +        error_setg_errno(errp, errno, "vfio_dma_unmap_vaddr_all");
>> +        return -errno;
>> +    }
>> +    return 0;
>> +}
>> +
>> +static int vfio_dma_map_vaddr(VFIOContainer *container, hwaddr iova,
>> +                              ram_addr_t size, void *vaddr,
>> +                              Error **errp)
>> +{
>> +    struct vfio_iommu_type1_dma_map map = {
>> +        .argsz = sizeof(map),
>> +        .flags = VFIO_DMA_MAP_FLAG_VADDR,
>> +        .vaddr = (__u64)(uintptr_t)vaddr,
>> +        .iova = iova,
>> +        .size = size,
>> +    };
>> +    if (ioctl(container->fd, VFIO_IOMMU_MAP_DMA, &map)) {
>> +        error_setg_errno(errp, errno,
>> +                         "vfio_dma_map_vaddr(iova %lu, size %ld, va %p)",
>> +                         iova, size, vaddr);
>> +        return -errno;
>> +    }
>> +    return 0;
>> +}
>> +
>> +static int
>> +vfio_region_remap(MemoryRegionSection *section, void *handle, Error **errp)
>> +{
>> +    MemoryRegion *mr = section->mr;
>> +    VFIOContainer *container = handle;
>> +    const char *name = memory_region_name(mr);
>> +    ram_addr_t size = int128_get64(section->size);
>> +    hwaddr offset, iova, roundup;
>> +    void *vaddr;
>> +
>> +    if (vfio_listener_skipped_section(section) || memory_region_is_iommu(mr)) {
> 
> A comment reminding us why we're also skipping iommu regions would be
> useful.  

OK.

> It's not clear to me why this needs to happen separately from
> the listener.  

After vfio_realize registers the address space listener, subsequent device realizations
can modify the address space.  After all realizations, qemu's picture of the address space
matches the kernel's picture of mapped dma ranges, and it is safe to call vfio_region_remap.
However, the intermediate qemu picture after each realization may not match the kernel's
picture, so we cannot allow the listener to issue incremental ioctl's.

> There's a sufficient degree of magic here that I'm
> afraid it's going to get broken too easily if it's left to me trying to
> remember how it's supposed to work.
>> +        return 0;
>> +    }
>> +
>> +    offset = section->offset_within_address_space;
>> +    iova = REAL_HOST_PAGE_ALIGN(offset);
>> +    roundup = iova - offset;
>> +    size -= roundup;
>> +    size = REAL_HOST_PAGE_ALIGN(size);
>> +    vaddr = memory_region_get_ram_ptr(mr) +
>> +            section->offset_within_region + roundup;
>> +
>> +    trace_vfio_region_remap(name, container->fd, iova, iova + size - 1, vaddr);
>> +    return vfio_dma_map_vaddr(container, iova, size, vaddr, errp);
>> +}
>> +
>> +bool vfio_is_cpr_capable(VFIOContainer *container, Error **errp)
>> +{
>> +    if (!ioctl(container->fd, VFIO_CHECK_EXTENSION, VFIO_UPDATE_VADDR) ||
>> +        !ioctl(container->fd, VFIO_CHECK_EXTENSION, VFIO_UNMAP_ALL)) {
>> +        error_setg(errp, "VFIO container does not support VFIO_UPDATE_VADDR "
>> +                         "or VFIO_UNMAP_ALL");
>> +        return false;
>> +    } else {
>> +        return true;
>> +    }
>> +}
>> +
>> +int vfio_cpr_save(Error **errp)
>> +{
>> +    ERRP_GUARD();
>> +    VFIOAddressSpace *space, *last_space;
>> +    VFIOContainer *container, *last_container;
>> +
>> +    QLIST_FOREACH(space, &vfio_address_spaces, list) {
>> +        QLIST_FOREACH(container, &space->containers, next) {
>> +            if (!vfio_is_cpr_capable(container, errp)) {
>> +                return -1;
>> +            }
>> +        }
>> +    }
>> +
>> +    QLIST_FOREACH(space, &vfio_address_spaces, list) {
>> +        QLIST_FOREACH(container, &space->containers, next) {
>> +            if (vfio_dma_unmap_vaddr_all(container, errp)) {
>> +                goto unwind;
>> +            }
>> +        }
>> +    }
>> +    return 0;
>> +
>> +unwind:
>> +    last_space = space;
>> +    last_container = container;
>> +    QLIST_FOREACH(space, &vfio_address_spaces, list) {
>> +        QLIST_FOREACH(container, &space->containers, next) {
>> +            Error *err;
>> +
>> +            if (space == last_space && container == last_container) {
>> +                break;
>> +            }
> 
> Isn't it sufficient to only test the container?  I think we'd be in
> trouble if we found a container on multiple address space lists.  Too

OK.

> bad we don't have a continue_reverse foreach or it might be trivial to
> convert to a qtailq. 
> 
>> +            if (address_space_flat_for_each_section(space->as,
>> +                                                    vfio_region_remap,
>> +                                                    container, &err)) {
>> +                error_prepend(errp, "%s", error_get_pretty(err));
>> +                error_free(err);
>> +            }
>> +        }
>> +    }
>> +    return -1;
>> +}
>> +
>> +int vfio_cpr_load(Error **errp)
>> +{
>> +    VFIOAddressSpace *space;
>> +    VFIOContainer *container;
>> +    VFIOGroup *group;
>> +    VFIODevice *vbasedev;
>> +
>> +    QLIST_FOREACH(space, &vfio_address_spaces, list) {
>> +        QLIST_FOREACH(container, &space->containers, next) {
>> +            if (!vfio_is_cpr_capable(container, errp)) {
>> +                return -1;
>> +            }
>> +            container->reused = false;
>> +            if (address_space_flat_for_each_section(space->as,
>> +                                                    vfio_region_remap,
>> +                                                    container, errp)) {
>> +                return -1;
>> +            }
>> +        }
>> +    }
>> +    QLIST_FOREACH(group, &vfio_group_list, next) {
>> +        QLIST_FOREACH(vbasedev, &group->device_list, next) {
>> +            vbasedev->reused = false;
>> +        }
>> +    }
> 
> The above is a bit disjoint between group/device and space/container,
> how about walking container->group_list rather than the global group
> list?

OK.

>> +    return 0;
>> +}
>> diff --git a/hw/vfio/meson.build b/hw/vfio/meson.build
>> index da9af29..e247b2b 100644
>> --- a/hw/vfio/meson.build
>> +++ b/hw/vfio/meson.build
>> @@ -5,6 +5,7 @@ vfio_ss.add(files(
>>    'migration.c',
>>  ))
>>  vfio_ss.add(when: 'CONFIG_VFIO_PCI', if_true: files(
>> +  'cpr.c',
>>    'display.c',
>>    'pci-quirks.c',
>>    'pci.c',
>> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
>> index e8e371e..64e2557 100644
>> --- a/hw/vfio/pci.c
>> +++ b/hw/vfio/pci.c
>> @@ -29,6 +29,7 @@
>>  #include "hw/qdev-properties.h"
>>  #include "hw/qdev-properties-system.h"
>>  #include "migration/vmstate.h"
>> +#include "migration/cpr.h"
>>  #include "qemu/error-report.h"
>>  #include "qemu/main-loop.h"
>>  #include "qemu/module.h"
>> @@ -2899,6 +2900,7 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
>>          vfio_put_group(group);
>>          goto error;
>>      }
>> +    pdev->reused = vdev->vbasedev.reused;
>>  
>>      vfio_populate_device(vdev, &err);
>>      if (err) {
>> @@ -3168,6 +3170,10 @@ static void vfio_pci_reset(DeviceState *dev)
>>  {
>>      VFIOPCIDevice *vdev = VFIO_PCI(dev);
>>  
>> +    if (vdev->pdev.reused) {
>> +        return;
>> +    }
> 
> Why are we the only ones using PCIDevice.reused and why are we testing
> that rather than VFIOPCIDevice.reused above?  These have different
> lifecycles and the difference is too subtle, esp. w/o comments.

PCIDevice.reused is referenced in hw/pci/pci.c:pci_do_device_reset().

I'll add a reused field to VFIOPCIDevice for use in the vfio specific code.

>> +
>>      trace_vfio_pci_reset(vdev->vbasedev.name);
>>  
>>      vfio_pci_pre_reset(vdev);
>> @@ -3275,6 +3281,56 @@ static Property vfio_pci_dev_properties[] = {
>>      DEFINE_PROP_END_OF_LIST(),
>>  };
>>  
>> +static void vfio_merge_config(VFIOPCIDevice *vdev)
>> +{
>> +    PCIDevice *pdev = &vdev->pdev;
>> +    int size = MIN(pci_config_size(pdev), vdev->config_size);
>> +    g_autofree uint8_t *phys_config = g_malloc(size);
>> +    uint32_t mask;
>> +    int ret, i;
>> +
>> +    ret = pread(vdev->vbasedev.fd, phys_config, size, vdev->config_offset);
>> +    if (ret < size) {
>> +        ret = ret < 0 ? errno : EFAULT;
>> +        error_report("failed to read device config space: %s", strerror(ret));
>> +        return;
>> +    }
>> +
>> +    for (i = 0; i < size; i++) {
>> +        mask = vdev->emulated_config_bits[i];
>> +        pdev->config[i] = (pdev->config[i] & mask) | (phys_config[i] & ~mask);
>> +    }
>> +}
>> +
>> +static int vfio_pci_post_load(void *opaque, int version_id)
>> +{
>> +    VFIOPCIDevice *vdev = opaque;
>> +    PCIDevice *pdev = &vdev->pdev;
>> +
>> +    vfio_merge_config(vdev);
>> +
>> +    pdev->reused = false;
>> +
>> +    return 0;
>> +}
>> +
>> +static bool vfio_pci_needed(void *opaque)
>> +{
>> +    return cpr_mode() == CPR_MODE_RESTART;
>> +}
>> +
>> +static const VMStateDescription vfio_pci_vmstate = {
>> +    .name = "vfio-pci",
>> +    .unmigratable = 1,
> 
> Doesn't this break the experimental (for now) migration support?

Yes, thanks.  I will delete this line and add a comment.  vfio_pci_needed() guarantees
that this handler is only used for cpr.

> 
>> +    .version_id = 0,
>> +    .minimum_version_id = 0,
>> +    .post_load = vfio_pci_post_load,
>> +    .needed = vfio_pci_needed,
>> +    .fields = (VMStateField[]) {
>> +        VMSTATE_END_OF_LIST()
>> +    }
>> +};
>> +
>>  static void vfio_pci_dev_class_init(ObjectClass *klass, void *data)
>>  {
>>      DeviceClass *dc = DEVICE_CLASS(klass);
>> @@ -3282,6 +3338,7 @@ static void vfio_pci_dev_class_init(ObjectClass *klass, void *data)
>>  
>>      dc->reset = vfio_pci_reset;
>>      device_class_set_props(dc, vfio_pci_dev_properties);
>> +    dc->vmsd = &vfio_pci_vmstate;
>>      dc->desc = "VFIO-based PCI device assignment";
>>      set_bit(DEVICE_CATEGORY_MISC, dc->categories);
>>      pdc->realize = vfio_realize;
>> [...]
>> diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h
>> index e680594..48a02c0 100644
>> --- a/linux-headers/linux/vfio.h
>> +++ b/linux-headers/linux/vfio.h
>> @@ -52,6 +52,12 @@
>>  /* Supports the vaddr flag for DMA map and unmap */
>>  #define VFIO_UPDATE_VADDR		10
>            ^^^^^^^^^^^^^^^^^
> 
> It's already there.  Thanks,

Thanks, I will delete that and the dup'd VFIO_UNMAP_ALL                        .

- Steve

>> +/* Supports VFIO_DMA_UNMAP_FLAG_ALL */
>> +#define VFIO_UNMAP_ALL                        9
>> +
>> +/* Supports VFIO DMA map and unmap with the VADDR flag */
>> +#define VFIO_UPDATE_VADDR              10
>> +

Zheng Chuan Nov. 10, 2021, 7:48 a.m. UTC | #3

Hi, steve

On 2021/8/11 1:06, Alex Williamson wrote:
> On Fri,  6 Aug 2021 14:43:53 -0700
> Steve Sistare <[e-mail]> wrote:
> 
>> Enable vfio-pci devices to be saved and restored across an exec restart
>> of qemu.
>>
>> At vfio creation time, save the value of vfio container, group, and device
>> descriptors in cpr state.
>>
>> In cpr-save and cpr-exec, suspend the use of virtual addresses in DMA
>> mappings with VFIO_DMA_UNMAP_FLAG_VADDR, because guest ram will be remapped
>> at a different VA after exec.  DMA to already-mapped pages continues.  Save
>> the msi message area as part of vfio-pci vmstate, save the interrupt and
>> notifier eventfd's in cpr state, and clear the close-on-exec flag for the
>> vfio descriptors.  The flag is not cleared earlier because the descriptors
>> should not persist across miscellaneous fork and exec calls that may be
>> performed during normal operation.
>>
>> On qemu restart, vfio_realize() finds the descriptor env vars, uses
>> the descriptors, and notes that the device is being reused.  Device and
>> iommu state is already configured, so operations in vfio_realize that
>> would modify the configuration are skipped for a reused device, including
>> vfio ioctl's and writes to PCI configuration space.  The result is that
>> vfio_realize constructs qemu data structures that reflect the current
>> state of the device.  However, the reconstruction is not complete until
>> cpr-load is called. cpr-load loads the msi data and finds eventfds in cpr
>> state.  It rebuilds vector data structures and attaches the interrupts to
>> the new KVM instance.  cpr-load then walks the flattened ranges of the
>> vfio_address_spaces and calls VFIO_DMA_MAP_FLAG_VADDR to inform the kernel
>> of the new VA's.  Lastly, it starts the VM and suppresses vfio device reset.
>>
>> This functionality is delivered by 3 patches for clarity.  Part 1 handles
>> device file descriptors and DMA.  Part 2 adds eventfd and MSI/MSI-X vector
>> support.  Part 3 adds INTX support.
>>
>> Signed-off-by: Steve Sistare <[e-mail]>
>> ---
>>  MAINTAINERS                   |   1 +
>>  hw/pci/pci.c                  |   4 ++
>>  hw/vfio/common.c              |  69 ++++++++++++++++--
>>  hw/vfio/cpr.c                 | 160 ++++++++++++++++++++++++++++++++++++++++++
>>  hw/vfio/meson.build           |   1 +
>>  hw/vfio/pci.c                 |  57 +++++++++++++++
>>  hw/vfio/trace-events          |   1 +
>>  include/hw/pci/pci.h          |   1 +
>>  include/hw/vfio/vfio-common.h |   5 ++
>>  include/migration/cpr.h       |   3 +
>>  linux-headers/linux/vfio.h    |   6 ++
>>  migration/cpr.c               |  10 ++-
>>  migration/target.c            |  14 ++++
>>  13 files changed, 325 insertions(+), 7 deletions(-)
>>  create mode 100644 hw/vfio/cpr.c
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index a9d2ed8..3132965 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -2904,6 +2904,7 @@ CPR
>>  M: Steve Sistare <[e-mail]>
>>  M: Mark Kanda <[e-mail]>
>>  S: Maintained
>> +F: hw/vfio/cpr.c
>>  F: include/migration/cpr.h
>>  F: migration/cpr.c
>>  F: qapi/cpr.json
>> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
>> index 59408a3..b9c6ca1 100644
>> --- a/hw/pci/pci.c
>> +++ b/hw/pci/pci.c
>> @@ -307,6 +307,10 @@ static void pci_do_device_reset(PCIDevice *dev)
>>  {
>>      int r;
>>  
>> +    if (dev->reused) {
>> +        return;
>> +    }
>> +
>>      pci_device_deassert_intx(dev);
>>      assert(dev->irq_state == 0);
>>  
>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
>> index 7918c0d..872a1ac 100644
>> --- a/hw/vfio/common.c
>> +++ b/hw/vfio/common.c
>> @@ -31,6 +31,7 @@
>>  #include "exec/memory.h"
>>  #include "exec/ram_addr.h"
>>  #include "hw/hw.h"
>> +#include "migration/cpr.h"
>>  #include "qemu/error-report.h"
>>  #include "qemu/main-loop.h"
>>  #include "qemu/range.h"
>> @@ -464,6 +465,10 @@ static int vfio_dma_unmap(VFIOContainer *container,
>>          return vfio_dma_unmap_bitmap(container, iova, size, iotlb);
>>      }
>>  
>> +    if (container->reused) {
>> +        return 0;
>> +    }
>> +
>>      while (ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, &unmap)) {
>>          /*
>>           * The type1 backend has an off-by-one bug in the kernel (71a7d3d78e3c
>> @@ -501,6 +506,10 @@ static int vfio_dma_map(VFIOContainer *container, hwaddr iova,
>>          .size = size,
>>      };
>>  
>> +    if (container->reused) {
>> +        return 0;
>> +    }
>> +
>>      if (!readonly) {
>>          map.flags |= VFIO_DMA_MAP_FLAG_WRITE;
>>      }
>> @@ -1872,6 +1881,10 @@ static int vfio_init_container(VFIOContainer *container, int group_fd,
>>      if (iommu_type < 0) {
>>          return iommu_type;
>>      }
>> +    if (container->reused) {
>> +        container->iommu_type = iommu_type;
>> +        return 0;
>> +    }
>>  
> 
> I'd like to see more comments throughout, but particularly where we're
> dumping out of functions for reused containers, groups, and devices.
> For instance map/unmap we're assuming we'll reach the same IOMMU
> mapping state we had previously, how do we validate that, why can't we
> only set vaddr in the mapping path rather than skipping it for a later
> pass at the flatmap, do we actually see unmaps, is deferring listener
> registration an alternate option, which specific reset path are we
> trying to defer, why are VFIOPCIDevices the only PCIDevices that set
> reused, there are some assumptions about the iommu_type that could use
> further description, etc.
> 
>>      ret = ioctl(group_fd, VFIO_GROUP_SET_CONTAINER, &container->fd);
>>      if (ret) {
>> @@ -1972,6 +1985,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>>  {
>>      VFIOContainer *container;
>>      int ret, fd;
>> +    bool reused;
>>      VFIOAddressSpace *space;
>>  
>>      space = vfio_get_address_space(as);
>> @@ -2007,7 +2021,13 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>>       * details once we know which type of IOMMU we are using.
>>       */
>>  
>> +    fd = cpr_find_fd("vfio_container_for_group", group->groupid);
>> +    reused = (fd >= 0);
>> +
>>      QLIST_FOREACH(container, &space->containers, next) {
>> +        if (container->fd == fd) {
>> +            break;
>> +        }
>>          if (!ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &container->fd)) {
> 
> 
> Letting the reused case call this ioctl feels a little sloppy.  I'm
> assuming we've tested this in a vIOMMU config or other setups where
> we'd actually have multiple containers and we're relying on the ioctl
> failing, but why call it at all if we already know the group is
> attached to a container.
> 
> 
>>              ret = vfio_ram_block_discard_disable(container, true);
>>              if (ret) {
>> @@ -2020,14 +2040,25 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>>                  }
>>                  return ret;
>>              }
>> -            group->container = container;
>> -            QLIST_INSERT_HEAD(&container->group_list, group, container_next);
>> +            break;
>> +        }
>> +    }
>> +
>> +    if (container) {
>> +        group->container = container;
>> +        QLIST_INSERT_HEAD(&container->group_list, group, container_next);
>> +        if (!reused) {
>>              vfio_kvm_device_add_group(group);
>> -            return 0;
>> +            cpr_save_fd("vfio_container_for_group", group->groupid,
>> +                        container->fd);
>>          }
>> +        return 0;
>> +    }
>> +
>> +    if (!reused) {
>> +        fd = qemu_open_old("/dev/vfio/vfio", O_RDWR);
>>      }
>>  
>> -    fd = qemu_open_old("/dev/vfio/vfio", O_RDWR);
>>      if (fd < 0) {
>>          error_setg_errno(errp, errno, "failed to open /dev/vfio/vfio");
>>          ret = -errno;
>> @@ -2045,6 +2076,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>>      container = g_malloc0(sizeof(*container));
>>      container->space = space;
>>      container->fd = fd;
>> +    container->reused = reused;
>>      container->error = NULL;
>>      container->dirty_pages_supported = false;
>>      container->dma_max_mappings = 0;
>> @@ -2183,6 +2215,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
>>      }
>>  
>>      container->initialized = true;
>> +    cpr_save_fd("vfio_container_for_group", group->groupid, fd);
>>  
>>      return 0;
>>  listener_release_exit:
>> @@ -2212,6 +2245,7 @@ static void vfio_disconnect_container(VFIOGroup *group)
>>  
>>      QLIST_REMOVE(group, container_next);
>>      group->container = NULL;
>> +    cpr_delete_fd("vfio_container_for_group", group->groupid);
>>  
>>      /*
>>       * Explicitly release the listener first before unset container,
>> @@ -2253,6 +2287,7 @@ VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp)
>>      VFIOGroup *group;
>>      char path[32];
>>      struct vfio_group_status status = { .argsz = sizeof(status) };
>> +    bool reused;
>>  
>>      QLIST_FOREACH(group, &vfio_group_list, next) {
>>          if (group->groupid == groupid) {
>> @@ -2270,7 +2305,13 @@ VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp)
>>      group = g_malloc0(sizeof(*group));
>>  
>>      snprintf(path, sizeof(path), "/dev/vfio/%d", groupid);
>> -    group->fd = qemu_open_old(path, O_RDWR);
>> +
>> +    group->fd = cpr_find_fd("vfio_group", groupid);
>> +    reused = (group->fd >= 0);
>> +    if (!reused) {
>> +        group->fd = qemu_open_old(path, O_RDWR);
>> +    }
>> +
>>      if (group->fd < 0) {
>>          error_setg_errno(errp, errno, "failed to open %s", path);
>>          goto free_group_exit;
>> @@ -2304,6 +2345,10 @@ VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp)
>>  
>>      QLIST_INSERT_HEAD(&vfio_group_list, group, next);
>>  
>> +    if (!reused) {
>> +        cpr_save_fd("vfio_group", groupid, group->fd);
>> +    }
>> +
>>      return group;
>>  
>>  close_fd_exit:
>> @@ -2328,6 +2373,7 @@ void vfio_put_group(VFIOGroup *group)
>>      vfio_disconnect_container(group);
>>      QLIST_REMOVE(group, next);
>>      trace_vfio_put_group(group->fd);
>> +    cpr_delete_fd("vfio_group", group->groupid);
>>      close(group->fd);
>>      g_free(group);
>>  
>> @@ -2341,8 +2387,14 @@ int vfio_get_device(VFIOGroup *group, const char *name,
>>  {
>>      struct vfio_device_info dev_info = { .argsz = sizeof(dev_info) };
>>      int ret, fd;
>> +    bool reused;
>> +
>> +    fd = cpr_find_fd(name, 0);
>> +    reused = (fd >= 0);
>> +    if (!reused) {
>> +        fd = ioctl(group->fd, VFIO_GROUP_GET_DEVICE_FD, name);
>> +    }
>>  
>> -    fd = ioctl(group->fd, VFIO_GROUP_GET_DEVICE_FD, name);
>>      if (fd < 0) {
>>          error_setg_errno(errp, errno, "error getting device from group %d",
>>                           group->groupid);
>> @@ -2387,6 +2439,10 @@ int vfio_get_device(VFIOGroup *group, const char *name,
>>      vbasedev->num_irqs = dev_info.num_irqs;
>>      vbasedev->num_regions = dev_info.num_regions;
>>      vbasedev->flags = dev_info.flags;
>> +    vbasedev->reused = reused;
>> +    if (!reused) {
>> +        cpr_save_fd(name, 0, fd);
>> +    }
>>  
>>      trace_vfio_get_device(name, dev_info.flags, dev_info.num_regions,
>>                            dev_info.num_irqs);
>> @@ -2403,6 +2459,7 @@ void vfio_put_base_device(VFIODevice *vbasedev)
>>      QLIST_REMOVE(vbasedev, next);
>>      vbasedev->group = NULL;
>>      trace_vfio_put_base_device(vbasedev->fd);
>> +    cpr_delete_fd(vbasedev->name, 0);
>>      close(vbasedev->fd);
>>  }
>>  
>> diff --git a/hw/vfio/cpr.c b/hw/vfio/cpr.c
>> new file mode 100644
>> index 0000000..0981d31
>> --- /dev/null
>> +++ b/hw/vfio/cpr.c
>> @@ -0,0 +1,160 @@
>> +/*
>> + * Copyright (c) 2021 Oracle and/or its affiliates.
>> + *
>> + * This work is licensed under the terms of the GNU GPL, version 2.
>> + * See the COPYING file in the top-level directory.
>> + */
>> +
>> +#include "qemu/osdep.h"
>> +#include <sys/ioctl.h>
>> +#include <linux/vfio.h>
>> +#include "hw/vfio/vfio-common.h"
>> +#include "sysemu/kvm.h"
>> +#include "qapi/error.h"
>> +#include "trace.h"
>> +
>> +static int
>> +vfio_dma_unmap_vaddr_all(VFIOContainer *container, Error **errp)
>> +{
>> +    struct vfio_iommu_type1_dma_unmap unmap = {
>> +        .argsz = sizeof(unmap),
>> +        .flags = VFIO_DMA_UNMAP_FLAG_VADDR | VFIO_DMA_UNMAP_FLAG_ALL,
>> +        .iova = 0,
>> +        .size = 0,
>> +    };
>> +    if (ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, &unmap)) {
>> +        error_setg_errno(errp, errno, "vfio_dma_unmap_vaddr_all");
>> +        return -errno;
>> +    }
>> +    return 0;
>> +}
>> +
>> +static int vfio_dma_map_vaddr(VFIOContainer *container, hwaddr iova,
>> +                              ram_addr_t size, void *vaddr,
>> +                              Error **errp)
>> +{
>> +    struct vfio_iommu_type1_dma_map map = {
>> +        .argsz = sizeof(map),
>> +        .flags = VFIO_DMA_MAP_FLAG_VADDR,
>> +        .vaddr = (__u64)(uintptr_t)vaddr,
>> +        .iova = iova,
>> +        .size = size,
>> +    };
>> +    if (ioctl(container->fd, VFIO_IOMMU_MAP_DMA, &map)) {
>> +        error_setg_errno(errp, errno,
>> +                         "vfio_dma_map_vaddr(iova %lu, size %ld, va %p)",
>> +                         iova, size, vaddr);
>> +        return -errno;
>> +    }
>> +    return 0;
>> +}
>> +
>> +static int
>> +vfio_region_remap(MemoryRegionSection *section, void *handle, Error **errp)
>> +{
>> +    MemoryRegion *mr = section->mr;
>> +    VFIOContainer *container = handle;
>> +    const char *name = memory_region_name(mr);
>> +    ram_addr_t size = int128_get64(section->size);
>> +    hwaddr offset, iova, roundup;
>> +    void *vaddr;
>> +
>> +    if (vfio_listener_skipped_section(section) || memory_region_is_iommu(mr)) {
> 
> A comment reminding us why we're also skipping iommu regions would be
> useful.  It's not clear to me why this needs to happen separately from
> the listener.  There's a sufficient degree of magic here that I'm
> afraid it's going to get broken too easily if it's left to me trying to
> remember how it's supposed to work.
> 
>> +        return 0;
>> +    }
>> +
>> +    offset = section->offset_within_address_space;
>> +    iova = REAL_HOST_PAGE_ALIGN(offset);
We should not do remap if it shares on host page with other structures.
I think a judgement like int128_ge((int128_make64(iova), llend)) in vfio_listener_region_add() should be also added here to check it,
otherwise it will remap no-exit dma which causes the live update failure.
diff --git a/hw/vfio/cpr.c b/hw/vfio/cpr.c
index 0981d31..d231841 100644
--- a/hw/vfio/cpr.c
+++ b/hw/vfio/cpr.c
@@ -58,13 +58,21 @@ vfio_region_remap(MemoryRegionSection *section, void *handle, Error **errp)
     ram_addr_t size = int128_get64(section->size);
     hwaddr offset, iova, roundup;
     void *vaddr;
-
+    Int128 llend;
+
     if (vfio_listener_skipped_section(section) || memory_region_is_iommu(mr)) {
         return 0;
     }

     offset = section->offset_within_address_space;
     iova = REAL_HOST_PAGE_ALIGN(offset);
+    llend = int128_make64(section->offset_within_address_space);
+    llend = int128_add(llend, section->size);
+    llend = int128_and(llend, int128_exts64(qemu_real_host_page_mask));
+    if (int128_ge(int128_make64(iova), llend)) {
+        return 0;
+    }
+
     roundup = iova - offset;
     size -= roundup;
     size = REAL_HOST_PAGE_ALIGN(size);

>> +    roundup = iova - offset;
>> +    size -= roundup;
>> +    size = REAL_HOST_PAGE_ALIGN(size);
>> +    vaddr = memory_region_get_ram_ptr(mr) +
>> +            section->offset_within_region + roundup;
>> +
>> +    trace_vfio_region_remap(name, container->fd, iova, iova + size - 1, vaddr);
>> +    return vfio_dma_map_vaddr(container, iova, size, vaddr, errp);
>> +}
>> +
>> +bool vfio_is_cpr_capable(VFIOContainer *container, Error **errp)
>> +{
>> +    if (!ioctl(container->fd, VFIO_CHECK_EXTENSION, VFIO_UPDATE_VADDR) ||
>> +        !ioctl(container->fd, VFIO_CHECK_EXTENSION, VFIO_UNMAP_ALL)) {
>> +        error_setg(errp, "VFIO container does not support VFIO_UPDATE_VADDR "
>> +                         "or VFIO_UNMAP_ALL");
>> +        return false;
>> +    } else {
>> +        return true;
>> +    }
>> +}
>> +
>> +int vfio_cpr_save(Error **errp)
>> +{
>> +    ERRP_GUARD();
>> +    VFIOAddressSpace *space, *last_space;
>> +    VFIOContainer *container, *last_container;
>> +
>> +    QLIST_FOREACH(space, &vfio_address_spaces, list) {
>> +        QLIST_FOREACH(container, &space->containers, next) {
>> +            if (!vfio_is_cpr_capable(container, errp)) {
>> +                return -1;
>> +            }
>> +        }
>> +    }
>> +
>> +    QLIST_FOREACH(space, &vfio_address_spaces, list) {
>> +        QLIST_FOREACH(container, &space->containers, next) {
>> +            if (vfio_dma_unmap_vaddr_all(container, errp)) {
>> +                goto unwind;
>> +            }
>> +        }
>> +    }
>> +    return 0;
>> +
>> +unwind:
>> +    last_space = space;
>> +    last_container = container;
>> +    QLIST_FOREACH(space, &vfio_address_spaces, list) {
>> +        QLIST_FOREACH(container, &space->containers, next) {
>> +            Error *err;
>> +
>> +            if (space == last_space && container == last_container) {
>> +                break;
>> +            }
> 
> Isn't it sufficient to only test the container?  I think we'd be in
> trouble if we found a container on multiple address space lists.  Too
> bad we don't have a continue_reverse foreach or it might be trivial to
> convert to a qtailq. 
> 
>> +            if (address_space_flat_for_each_section(space->as,
>> +                                                    vfio_region_remap,
>> +                                                    container, &err)) {
>> +                error_prepend(errp, "%s", error_get_pretty(err));
>> +                error_free(err);
>> +            }
>> +        }
>> +    }
>> +    return -1;
>> +}
>> +
>> +int vfio_cpr_load(Error **errp)
>> +{
>> +    VFIOAddressSpace *space;
>> +    VFIOContainer *container;
>> +    VFIOGroup *group;
>> +    VFIODevice *vbasedev;
>> +
>> +    QLIST_FOREACH(space, &vfio_address_spaces, list) {
>> +        QLIST_FOREACH(container, &space->containers, next) {
>> +            if (!vfio_is_cpr_capable(container, errp)) {
>> +                return -1;
>> +            }
>> +            container->reused = false;
>> +            if (address_space_flat_for_each_section(space->as,
>> +                                                    vfio_region_remap,
>> +                                                    container, errp)) {
>> +                return -1;
>> +            }
>> +        }
>> +    }
>> +    QLIST_FOREACH(group, &vfio_group_list, next) {
>> +        QLIST_FOREACH(vbasedev, &group->device_list, next) {
>> +            vbasedev->reused = false;
>> +        }
>> +    }
> 
> The above is a bit disjoint between group/device and space/container,
> how about walking container->group_list rather than the global group
> list?
> 
>> +    return 0;
>> +}
>> diff --git a/hw/vfio/meson.build b/hw/vfio/meson.build
>> index da9af29..e247b2b 100644
>> --- a/hw/vfio/meson.build
>> +++ b/hw/vfio/meson.build
>> @@ -5,6 +5,7 @@ vfio_ss.add(files(
>>    'migration.c',
>>  ))
>>  vfio_ss.add(when: 'CONFIG_VFIO_PCI', if_true: files(
>> +  'cpr.c',
>>    'display.c',
>>    'pci-quirks.c',
>>    'pci.c',
>> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
>> index e8e371e..64e2557 100644
>> --- a/hw/vfio/pci.c
>> +++ b/hw/vfio/pci.c
>> @@ -29,6 +29,7 @@
>>  #include "hw/qdev-properties.h"
>>  #include "hw/qdev-properties-system.h"
>>  #include "migration/vmstate.h"
>> +#include "migration/cpr.h"
>>  #include "qemu/error-report.h"
>>  #include "qemu/main-loop.h"
>>  #include "qemu/module.h"
>> @@ -2899,6 +2900,7 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
>>          vfio_put_group(group);
>>          goto error;
>>      }
>> +    pdev->reused = vdev->vbasedev.reused;
>>  
>>      vfio_populate_device(vdev, &err);
>>      if (err) {
>> @@ -3168,6 +3170,10 @@ static void vfio_pci_reset(DeviceState *dev)
>>  {
>>      VFIOPCIDevice *vdev = VFIO_PCI(dev);
>>  
>> +    if (vdev->pdev.reused) {
>> +        return;
>> +    }
> 
> Why are we the only ones using PCIDevice.reused and why are we testing
> that rather than VFIOPCIDevice.reused above?  These have different
> lifecycles and the difference is too subtle, esp. w/o comments.
> 
>> +
>>      trace_vfio_pci_reset(vdev->vbasedev.name);
>>  
>>      vfio_pci_pre_reset(vdev);
>> @@ -3275,6 +3281,56 @@ static Property vfio_pci_dev_properties[] = {
>>      DEFINE_PROP_END_OF_LIST(),
>>  };
>>  
>> +static void vfio_merge_config(VFIOPCIDevice *vdev)
>> +{
>> +    PCIDevice *pdev = &vdev->pdev;
>> +    int size = MIN(pci_config_size(pdev), vdev->config_size);
>> +    g_autofree uint8_t *phys_config = g_malloc(size);
>> +    uint32_t mask;
>> +    int ret, i;
>> +
>> +    ret = pread(vdev->vbasedev.fd, phys_config, size, vdev->config_offset);
>> +    if (ret < size) {
>> +        ret = ret < 0 ? errno : EFAULT;
>> +        error_report("failed to read device config space: %s", strerror(ret));
>> +        return;
>> +    }
>> +
>> +    for (i = 0; i < size; i++) {
>> +        mask = vdev->emulated_config_bits[i];
>> +        pdev->config[i] = (pdev->config[i] & mask) | (phys_config[i] & ~mask);
>> +    }
>> +}
>> +
>> +static int vfio_pci_post_load(void *opaque, int version_id)
>> +{
>> +    VFIOPCIDevice *vdev = opaque;
>> +    PCIDevice *pdev = &vdev->pdev;
>> +
>> +    vfio_merge_config(vdev);
>> +
>> +    pdev->reused = false;
>> +
>> +    return 0;
>> +}
>> +
>> +static bool vfio_pci_needed(void *opaque)
>> +{
>> +    return cpr_mode() == CPR_MODE_RESTART;
>> +}
>> +
>> +static const VMStateDescription vfio_pci_vmstate = {
>> +    .name = "vfio-pci",
>> +    .unmigratable = 1,
> 
> 
> Doesn't this break the experimental (for now) migration support?
> 
> 
>> +    .version_id = 0,
>> +    .minimum_version_id = 0,
>> +    .post_load = vfio_pci_post_load,
>> +    .needed = vfio_pci_needed,
>> +    .fields = (VMStateField[]) {
>> +        VMSTATE_END_OF_LIST()
>> +    }
>> +};
>> +
>>  static void vfio_pci_dev_class_init(ObjectClass *klass, void *data)
>>  {
>>      DeviceClass *dc = DEVICE_CLASS(klass);
>> @@ -3282,6 +3338,7 @@ static void vfio_pci_dev_class_init(ObjectClass *klass, void *data)
>>  
>>      dc->reset = vfio_pci_reset;
>>      device_class_set_props(dc, vfio_pci_dev_properties);
>> +    dc->vmsd = &vfio_pci_vmstate;
>>      dc->desc = "VFIO-based PCI device assignment";
>>      set_bit(DEVICE_CATEGORY_MISC, dc->categories);
>>      pdc->realize = vfio_realize;
>> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
>> index 0ef1b5f..63dd0fe 100644
>> --- a/hw/vfio/trace-events
>> +++ b/hw/vfio/trace-events
>> @@ -118,6 +118,7 @@ vfio_region_sparse_mmap_header(const char *name, int index, int nr_areas) "Devic
>>  vfio_region_sparse_mmap_entry(int i, unsigned long start, unsigned long end) "sparse entry %d [0x%lx - 0x%lx]"
>>  vfio_get_dev_region(const char *name, int index, uint32_t type, uint32_t subtype) "%s index %d, %08x/%0x8"
>>  vfio_dma_unmap_overflow_workaround(void) ""
>> +vfio_region_remap(const char *name, int fd, uint64_t iova_start, uint64_t iova_end, void *vaddr) "%s fd %d 0x%"PRIx64" - 0x%"PRIx64" [%p]"
>>  
>>  # platform.c
>>  vfio_platform_base_device_init(char *name, int groupid) "%s belongs to group #%d"
>> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
>> index bf5be06..f079423 100644
>> --- a/include/hw/pci/pci.h
>> +++ b/include/hw/pci/pci.h
>> @@ -360,6 +360,7 @@ struct PCIDevice {
>>      /* ID of standby device in net_failover pair */
>>      char *failover_pair_id;
>>      uint32_t acpi_index;
>> +    bool reused;
>>  };
>>  
>>  void pci_register_bar(PCIDevice *pci_dev, int region_num,
>> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
>> index cb04cc6..0766cc4 100644
>> --- a/include/hw/vfio/vfio-common.h
>> +++ b/include/hw/vfio/vfio-common.h
>> @@ -85,6 +85,7 @@ typedef struct VFIOContainer {
>>      Error *error;
>>      bool initialized;
>>      bool dirty_pages_supported;
>> +    bool reused;
>>      uint64_t dirty_pgsizes;
>>      uint64_t max_dirty_bitmap_size;
>>      unsigned long pgsizes;
>> @@ -136,6 +137,7 @@ typedef struct VFIODevice {
>>      bool no_mmap;
>>      bool ram_block_discard_allowed;
>>      bool enable_migration;
>> +    bool reused;
>>      VFIODeviceOps *ops;
>>      unsigned int num_irqs;
>>      unsigned int num_regions;
>> @@ -212,6 +214,9 @@ VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp);
>>  void vfio_put_group(VFIOGroup *group);
>>  int vfio_get_device(VFIOGroup *group, const char *name,
>>                      VFIODevice *vbasedev, Error **errp);
>> +int vfio_cpr_save(Error **errp);
>> +int vfio_cpr_load(Error **errp);
>> +bool vfio_is_cpr_capable(VFIOContainer *container, Error **errp);
>>  
>>  extern const MemoryRegionOps vfio_region_ops;
>>  typedef QLIST_HEAD(VFIOGroupList, VFIOGroup) VFIOGroupList;
>> diff --git a/include/migration/cpr.h b/include/migration/cpr.h
>> index 83f69c9..e9b987f 100644
>> --- a/include/migration/cpr.h
>> +++ b/include/migration/cpr.h
>> @@ -25,4 +25,7 @@ int cpr_state_load(Error **errp);
>>  CprMode cpr_state_mode(void);
>>  void cpr_state_print(void);
>>  
>> +int cpr_vfio_save(Error **errp);
>> +int cpr_vfio_load(Error **errp);
>> +
>>  #endif
>> diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h
>> index e680594..48a02c0 100644
>> --- a/linux-headers/linux/vfio.h
>> +++ b/linux-headers/linux/vfio.h
>> @@ -52,6 +52,12 @@
>>  /* Supports the vaddr flag for DMA map and unmap */
>>  #define VFIO_UPDATE_VADDR		10
>            ^^^^^^^^^^^^^^^^^
> 
> It's already there.  Thanks,
> 
> Alex
> 
>>  
>> +/* Supports VFIO_DMA_UNMAP_FLAG_ALL */
>> +#define VFIO_UNMAP_ALL                        9
>> +
>> +/* Supports VFIO DMA map and unmap with the VADDR flag */
>> +#define VFIO_UPDATE_VADDR              10
>> +
>>  /*
>>   * The IOCTL interface is designed for extensibility by embedding the
>>   * structure length (argsz) and flags into structures passed between
>> diff --git a/migration/cpr.c b/migration/cpr.c
>> index 72a5f4b..16f11bd 100644
>> --- a/migration/cpr.c
>> +++ b/migration/cpr.c
>> @@ -7,6 +7,7 @@
>>  
>>  #include "qemu/osdep.h"
>>  #include "exec/memory.h"
>> +#include "hw/vfio/vfio-common.h"
>>  #include "io/channel-buffer.h"
>>  #include "io/channel-file.h"
>>  #include "migration.h"
>> @@ -108,7 +109,9 @@ void qmp_cpr_exec(strList *args, Error **errp)
>>          error_setg(errp, "cpr-exec requires cpr-save with restart mode");
>>          return;
>>      }
>> -
>> +    if (cpr_vfio_save(errp)) {
>> +        return;
>> +    }
>>      cpr_walk_fd(preserve_fd, 0);
>>      if (cpr_state_save(errp)) {
>>          return;
>> @@ -148,6 +151,11 @@ void qmp_cpr_load(const char *filename, Error **errp)
>>          goto out;
>>      }
>>  
>> +    if (cpr_active_mode == CPR_MODE_RESTART &&
>> +        cpr_vfio_load(errp)) {
>> +        goto out;
>> +    }
>> +
>>      state = global_state_get_runstate();
>>      if (state == RUN_STATE_RUNNING) {
>>          vm_start();
>> diff --git a/migration/target.c b/migration/target.c
>> index 4390bf0..984bc9e 100644
>> --- a/migration/target.c
>> +++ b/migration/target.c
>> @@ -8,6 +8,7 @@
>>  #include "qemu/osdep.h"
>>  #include "qapi/qapi-types-migration.h"
>>  #include "migration.h"
>> +#include "migration/cpr.h"
>>  #include CONFIG_DEVICES
>>  
>>  #ifdef CONFIG_VFIO
>> @@ -22,8 +23,21 @@ void populate_vfio_info(MigrationInfo *info)
>>          info->vfio->transferred = vfio_mig_bytes_transferred();
>>      }
>>  }
>> +
>> +int cpr_vfio_save(Error **errp)
>> +{
>> +    return vfio_cpr_save(errp);
>> +}
>> +
>> +int cpr_vfio_load(Error **errp)
>> +{
>> +    return vfio_cpr_load(errp);
>> +}
>> +
>>  #else
>>  
>>  void populate_vfio_info(MigrationInfo *info) {}
>> +int cpr_vfio_save(Error **errp) { return 0; }
>> +int cpr_vfio_load(Error **errp) { return 0; }
>>  
>>  #endif /* CONFIG_VFIO */
> 
> .
>

Steven Sistare Nov. 30, 2021, 4:11 p.m. UTC | #4

On 11/10/2021 2:48 AM, Zheng Chuan wrote:
> 
> Hi, steve
> 
> On 2021/8/11 1:06, Alex Williamson wrote:
>> On Fri,  6 Aug 2021 14:43:53 -0700
>> Steve Sistare <[e-mail]> wrote:
>> [...]
>>> +static int
>>> +vfio_region_remap(MemoryRegionSection *section, void *handle, Error **errp)
>>> +{
>>> +    MemoryRegion *mr = section->mr;
>>> +    VFIOContainer *container = handle;
>>> +    const char *name = memory_region_name(mr);
>>> +    ram_addr_t size = int128_get64(section->size);
>>> +    hwaddr offset, iova, roundup;
>>> +    void *vaddr;
>>> +
>>> +    if (vfio_listener_skipped_section(section) || memory_region_is_iommu(mr)) {
>>> +        return 0;
>>> +    }
>>> +
>>> +    offset = section->offset_within_address_space;
>>> +    iova = REAL_HOST_PAGE_ALIGN(offset);
> We should not do remap if it shares on host page with other structures.
> I think a judgement like int128_ge((int128_make64(iova), llend)) in vfio_listener_region_add() should be also added here to check it,
> otherwise it will remap no-exit dma which causes the live update failure.
> diff --git a/hw/vfio/cpr.c b/hw/vfio/cpr.c
> index 0981d31..d231841 100644
> --- a/hw/vfio/cpr.c
> +++ b/hw/vfio/cpr.c
> @@ -58,13 +58,21 @@ vfio_region_remap(MemoryRegionSection *section, void *handle, Error **errp)
>      ram_addr_t size = int128_get64(section->size);
>      hwaddr offset, iova, roundup;
>      void *vaddr;
> -
> +    Int128 llend;
> +
>      if (vfio_listener_skipped_section(section) || memory_region_is_iommu(mr)) {
>          return 0;
>      }
> 
>      offset = section->offset_within_address_space;
>      iova = REAL_HOST_PAGE_ALIGN(offset);
> +    llend = int128_make64(section->offset_within_address_space);
> +    llend = int128_add(llend, section->size);
> +    llend = int128_and(llend, int128_exts64(qemu_real_host_page_mask));
> +    if (int128_ge(int128_make64(iova), llend)) {
> +        return 0;
> +    }
> +
>      roundup = iova - offset;
>      size -= roundup;
>      size = REAL_HOST_PAGE_ALIGN(size);
> 
>>> +    roundup = iova - offset;
>>> +    size -= roundup;
>>> +    size = REAL_HOST_PAGE_ALIGN(size);
>>> +    vaddr = memory_region_get_ram_ptr(mr) +
>>> +            section->offset_within_region + roundup;
>>> +
>>> +    trace_vfio_region_remap(name, container->fd, iova, iova + size - 1, vaddr);
>>> +    return vfio_dma_map_vaddr(container, iova, size, vaddr, errp);
>>> +}

Thank you Zheng.  I intended to implement the logic you suggest, using 64-bit arithmetic,
but I botched it.  This should do the trick:

diff --git a/hw/vfio/cpr.c b/hw/vfio/cpr.c
index df334d9..bbdeaea 100644
--- a/hw/vfio/cpr.c
+++ b/hw/vfio/cpr.c
@@ -66,8 +66,8 @@ vfio_region_remap(MemoryRegionSection *section, void *handle,
     offset = section->offset_within_address_space;
     iova = REAL_HOST_PAGE_ALIGN(offset);
     roundup = iova - offset;
-    size -= roundup;
-    size = REAL_HOST_PAGE_ALIGN(size);
+    size -= roundup;                    /* adjust for starting alignment */
+    size &= qemu_real_host_page_mask;   /* adjust for ending alignment */
     end = iova + size;
     if (iova >= end) {
         return 0;

- Steve

Patch

diff --git a/MAINTAINERS b/MAINTAINERS
index a9d2ed8..3132965 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2904,6 +2904,7 @@  CPR
 M: Steve Sistare <[e-mail]>
 M: Mark Kanda <[e-mail]>
 S: Maintained
+F: hw/vfio/cpr.c
 F: include/migration/cpr.h
 F: migration/cpr.c
 F: qapi/cpr.json
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 59408a3..b9c6ca1 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -307,6 +307,10 @@  static void pci_do_device_reset(PCIDevice *dev)
 {
     int r;
 
+    if (dev->reused) {
+        return;
+    }
+
     pci_device_deassert_intx(dev);
     assert(dev->irq_state == 0);
 
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 7918c0d..872a1ac 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -31,6 +31,7 @@ 
 #include "exec/memory.h"
 #include "exec/ram_addr.h"
 #include "hw/hw.h"
+#include "migration/cpr.h"
 #include "qemu/error-report.h"
 #include "qemu/main-loop.h"
 #include "qemu/range.h"
@@ -464,6 +465,10 @@  static int vfio_dma_unmap(VFIOContainer *container,
         return vfio_dma_unmap_bitmap(container, iova, size, iotlb);
     }
 
+    if (container->reused) {
+        return 0;
+    }
+
     while (ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, &unmap)) {
         /*
          * The type1 backend has an off-by-one bug in the kernel (71a7d3d78e3c
@@ -501,6 +506,10 @@  static int vfio_dma_map(VFIOContainer *container, hwaddr iova,
         .size = size,
     };
 
+    if (container->reused) {
+        return 0;
+    }
+
     if (!readonly) {
         map.flags |= VFIO_DMA_MAP_FLAG_WRITE;
     }
@@ -1872,6 +1881,10 @@  static int vfio_init_container(VFIOContainer *container, int group_fd,
     if (iommu_type < 0) {
         return iommu_type;
     }
+    if (container->reused) {
+        container->iommu_type = iommu_type;
+        return 0;
+    }
 
     ret = ioctl(group_fd, VFIO_GROUP_SET_CONTAINER, &container->fd);
     if (ret) {
@@ -1972,6 +1985,7 @@  static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
 {
     VFIOContainer *container;
     int ret, fd;
+    bool reused;
     VFIOAddressSpace *space;
 
     space = vfio_get_address_space(as);
@@ -2007,7 +2021,13 @@  static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
      * details once we know which type of IOMMU we are using.
      */
 
+    fd = cpr_find_fd("vfio_container_for_group", group->groupid);
+    reused = (fd >= 0);
+
     QLIST_FOREACH(container, &space->containers, next) {
+        if (container->fd == fd) {
+            break;
+        }
         if (!ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &container->fd)) {
             ret = vfio_ram_block_discard_disable(container, true);
             if (ret) {
@@ -2020,14 +2040,25 @@  static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
                 }
                 return ret;
             }
-            group->container = container;
-            QLIST_INSERT_HEAD(&container->group_list, group, container_next);
+            break;
+        }
+    }
+
+    if (container) {
+        group->container = container;
+        QLIST_INSERT_HEAD(&container->group_list, group, container_next);
+        if (!reused) {
             vfio_kvm_device_add_group(group);
-            return 0;
+            cpr_save_fd("vfio_container_for_group", group->groupid,
+                        container->fd);
         }
+        return 0;
+    }
+
+    if (!reused) {
+        fd = qemu_open_old("/dev/vfio/vfio", O_RDWR);
     }
 
-    fd = qemu_open_old("/dev/vfio/vfio", O_RDWR);
     if (fd < 0) {
         error_setg_errno(errp, errno, "failed to open /dev/vfio/vfio");
         ret = -errno;
@@ -2045,6 +2076,7 @@  static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
     container = g_malloc0(sizeof(*container));
     container->space = space;
     container->fd = fd;
+    container->reused = reused;
     container->error = NULL;
     container->dirty_pages_supported = false;
     container->dma_max_mappings = 0;
@@ -2183,6 +2215,7 @@  static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
     }
 
     container->initialized = true;
+    cpr_save_fd("vfio_container_for_group", group->groupid, fd);
 
     return 0;
 listener_release_exit:
@@ -2212,6 +2245,7 @@  static void vfio_disconnect_container(VFIOGroup *group)
 
     QLIST_REMOVE(group, container_next);
     group->container = NULL;
+    cpr_delete_fd("vfio_container_for_group", group->groupid);
 
     /*
      * Explicitly release the listener first before unset container,
@@ -2253,6 +2287,7 @@  VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp)
     VFIOGroup *group;
     char path[32];
     struct vfio_group_status status = { .argsz = sizeof(status) };
+    bool reused;
 
     QLIST_FOREACH(group, &vfio_group_list, next) {
         if (group->groupid == groupid) {
@@ -2270,7 +2305,13 @@  VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp)
     group = g_malloc0(sizeof(*group));
 
     snprintf(path, sizeof(path), "/dev/vfio/%d", groupid);
-    group->fd = qemu_open_old(path, O_RDWR);
+
+    group->fd = cpr_find_fd("vfio_group", groupid);
+    reused = (group->fd >= 0);
+    if (!reused) {
+        group->fd = qemu_open_old(path, O_RDWR);
+    }
+
     if (group->fd < 0) {
         error_setg_errno(errp, errno, "failed to open %s", path);
         goto free_group_exit;
@@ -2304,6 +2345,10 @@  VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp)
 
     QLIST_INSERT_HEAD(&vfio_group_list, group, next);
 
+    if (!reused) {
+        cpr_save_fd("vfio_group", groupid, group->fd);
+    }
+
     return group;
 
 close_fd_exit:
@@ -2328,6 +2373,7 @@  void vfio_put_group(VFIOGroup *group)
     vfio_disconnect_container(group);
     QLIST_REMOVE(group, next);
     trace_vfio_put_group(group->fd);
+    cpr_delete_fd("vfio_group", group->groupid);
     close(group->fd);
     g_free(group);
 
@@ -2341,8 +2387,14 @@  int vfio_get_device(VFIOGroup *group, const char *name,
 {
     struct vfio_device_info dev_info = { .argsz = sizeof(dev_info) };
     int ret, fd;
+    bool reused;
+
+    fd = cpr_find_fd(name, 0);
+    reused = (fd >= 0);
+    if (!reused) {
+        fd = ioctl(group->fd, VFIO_GROUP_GET_DEVICE_FD, name);
+    }
 
-    fd = ioctl(group->fd, VFIO_GROUP_GET_DEVICE_FD, name);
     if (fd < 0) {
         error_setg_errno(errp, errno, "error getting device from group %d",
                          group->groupid);
@@ -2387,6 +2439,10 @@  int vfio_get_device(VFIOGroup *group, const char *name,
     vbasedev->num_irqs = dev_info.num_irqs;
     vbasedev->num_regions = dev_info.num_regions;
     vbasedev->flags = dev_info.flags;
+    vbasedev->reused = reused;
+    if (!reused) {
+        cpr_save_fd(name, 0, fd);
+    }
 
     trace_vfio_get_device(name, dev_info.flags, dev_info.num_regions,
                           dev_info.num_irqs);
@@ -2403,6 +2459,7 @@  void vfio_put_base_device(VFIODevice *vbasedev)
     QLIST_REMOVE(vbasedev, next);
     vbasedev->group = NULL;
     trace_vfio_put_base_device(vbasedev->fd);
+    cpr_delete_fd(vbasedev->name, 0);
     close(vbasedev->fd);
 }
 
diff --git a/hw/vfio/cpr.c b/hw/vfio/cpr.c
new file mode 100644
index 0000000..0981d31
--- /dev/null
+++ b/hw/vfio/cpr.c
@@ -0,0 +1,160 @@ 
+/*
+ * Copyright (c) 2021 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include <sys/ioctl.h>
+#include <linux/vfio.h>
+#include "hw/vfio/vfio-common.h"
+#include "sysemu/kvm.h"
+#include "qapi/error.h"
+#include "trace.h"
+
+static int
+vfio_dma_unmap_vaddr_all(VFIOContainer *container, Error **errp)
+{
+    struct vfio_iommu_type1_dma_unmap unmap = {
+        .argsz = sizeof(unmap),
+        .flags = VFIO_DMA_UNMAP_FLAG_VADDR | VFIO_DMA_UNMAP_FLAG_ALL,
+        .iova = 0,
+        .size = 0,
+    };
+    if (ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, &unmap)) {
+        error_setg_errno(errp, errno, "vfio_dma_unmap_vaddr_all");
+        return -errno;
+    }
+    return 0;
+}
+
+static int vfio_dma_map_vaddr(VFIOContainer *container, hwaddr iova,
+                              ram_addr_t size, void *vaddr,
+                              Error **errp)
+{
+    struct vfio_iommu_type1_dma_map map = {
+        .argsz = sizeof(map),
+        .flags = VFIO_DMA_MAP_FLAG_VADDR,
+        .vaddr = (__u64)(uintptr_t)vaddr,
+        .iova = iova,
+        .size = size,
+    };
+    if (ioctl(container->fd, VFIO_IOMMU_MAP_DMA, &map)) {
+        error_setg_errno(errp, errno,
+                         "vfio_dma_map_vaddr(iova %lu, size %ld, va %p)",
+                         iova, size, vaddr);
+        return -errno;
+    }
+    return 0;
+}
+
+static int
+vfio_region_remap(MemoryRegionSection *section, void *handle, Error **errp)
+{
+    MemoryRegion *mr = section->mr;
+    VFIOContainer *container = handle;
+    const char *name = memory_region_name(mr);
+    ram_addr_t size = int128_get64(section->size);
+    hwaddr offset, iova, roundup;
+    void *vaddr;
+
+    if (vfio_listener_skipped_section(section) || memory_region_is_iommu(mr)) {
+        return 0;
+    }
+
+    offset = section->offset_within_address_space;
+    iova = REAL_HOST_PAGE_ALIGN(offset);
+    roundup = iova - offset;
+    size -= roundup;
+    size = REAL_HOST_PAGE_ALIGN(size);
+    vaddr = memory_region_get_ram_ptr(mr) +
+            section->offset_within_region + roundup;
+
+    trace_vfio_region_remap(name, container->fd, iova, iova + size - 1, vaddr);
+    return vfio_dma_map_vaddr(container, iova, size, vaddr, errp);
+}
+
+bool vfio_is_cpr_capable(VFIOContainer *container, Error **errp)
+{
+    if (!ioctl(container->fd, VFIO_CHECK_EXTENSION, VFIO_UPDATE_VADDR) ||
+        !ioctl(container->fd, VFIO_CHECK_EXTENSION, VFIO_UNMAP_ALL)) {
+        error_setg(errp, "VFIO container does not support VFIO_UPDATE_VADDR "
+                         "or VFIO_UNMAP_ALL");
+        return false;
+    } else {
+        return true;
+    }
+}
+
+int vfio_cpr_save(Error **errp)
+{
+    ERRP_GUARD();
+    VFIOAddressSpace *space, *last_space;
+    VFIOContainer *container, *last_container;
+
+    QLIST_FOREACH(space, &vfio_address_spaces, list) {
+        QLIST_FOREACH(container, &space->containers, next) {
+            if (!vfio_is_cpr_capable(container, errp)) {
+                return -1;
+            }
+        }
+    }
+
+    QLIST_FOREACH(space, &vfio_address_spaces, list) {
+        QLIST_FOREACH(container, &space->containers, next) {
+            if (vfio_dma_unmap_vaddr_all(container, errp)) {
+                goto unwind;
+            }
+        }
+    }
+    return 0;
+
+unwind:
+    last_space = space;
+    last_container = container;
+    QLIST_FOREACH(space, &vfio_address_spaces, list) {
+        QLIST_FOREACH(container, &space->containers, next) {
+            Error *err;
+
+            if (space == last_space && container == last_container) {
+                break;
+            }
+            if (address_space_flat_for_each_section(space->as,
+                                                    vfio_region_remap,
+                                                    container, &err)) {
+                error_prepend(errp, "%s", error_get_pretty(err));
+                error_free(err);
+            }
+        }
+    }
+    return -1;
+}
+
+int vfio_cpr_load(Error **errp)
+{
+    VFIOAddressSpace *space;
+    VFIOContainer *container;
+    VFIOGroup *group;
+    VFIODevice *vbasedev;
+
+    QLIST_FOREACH(space, &vfio_address_spaces, list) {
+        QLIST_FOREACH(container, &space->containers, next) {
+            if (!vfio_is_cpr_capable(container, errp)) {
+                return -1;
+            }
+            container->reused = false;
+            if (address_space_flat_for_each_section(space->as,
+                                                    vfio_region_remap,
+                                                    container, errp)) {
+                return -1;
+            }
+        }
+    }
+    QLIST_FOREACH(group, &vfio_group_list, next) {
+        QLIST_FOREACH(vbasedev, &group->device_list, next) {
+            vbasedev->reused = false;
+        }
+    }
+    return 0;
+}
diff --git a/hw/vfio/meson.build b/hw/vfio/meson.build
index da9af29..e247b2b 100644
--- a/hw/vfio/meson.build
+++ b/hw/vfio/meson.build
@@ -5,6 +5,7 @@  vfio_ss.add(files(
   'migration.c',
 ))
 vfio_ss.add(when: 'CONFIG_VFIO_PCI', if_true: files(
+  'cpr.c',
   'display.c',
   'pci-quirks.c',
   'pci.c',
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index e8e371e..64e2557 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -29,6 +29,7 @@ 
 #include "hw/qdev-properties.h"
 #include "hw/qdev-properties-system.h"
 #include "migration/vmstate.h"
+#include "migration/cpr.h"
 #include "qemu/error-report.h"
 #include "qemu/main-loop.h"
 #include "qemu/module.h"
@@ -2899,6 +2900,7 @@  static void vfio_realize(PCIDevice *pdev, Error **errp)
         vfio_put_group(group);
         goto error;
     }
+    pdev->reused = vdev->vbasedev.reused;
 
     vfio_populate_device(vdev, &err);
     if (err) {
@@ -3168,6 +3170,10 @@  static void vfio_pci_reset(DeviceState *dev)
 {
     VFIOPCIDevice *vdev = VFIO_PCI(dev);
 
+    if (vdev->pdev.reused) {
+        return;
+    }
+
     trace_vfio_pci_reset(vdev->vbasedev.name);
 
     vfio_pci_pre_reset(vdev);
@@ -3275,6 +3281,56 @@  static Property vfio_pci_dev_properties[] = {
     DEFINE_PROP_END_OF_LIST(),
 };
 
+static void vfio_merge_config(VFIOPCIDevice *vdev)
+{
+    PCIDevice *pdev = &vdev->pdev;
+    int size = MIN(pci_config_size(pdev), vdev->config_size);
+    g_autofree uint8_t *phys_config = g_malloc(size);
+    uint32_t mask;
+    int ret, i;
+
+    ret = pread(vdev->vbasedev.fd, phys_config, size, vdev->config_offset);
+    if (ret < size) {
+        ret = ret < 0 ? errno : EFAULT;
+        error_report("failed to read device config space: %s", strerror(ret));
+        return;
+    }
+
+    for (i = 0; i < size; i++) {
+        mask = vdev->emulated_config_bits[i];
+        pdev->config[i] = (pdev->config[i] & mask) | (phys_config[i] & ~mask);
+    }
+}
+
+static int vfio_pci_post_load(void *opaque, int version_id)
+{
+    VFIOPCIDevice *vdev = opaque;
+    PCIDevice *pdev = &vdev->pdev;
+
+    vfio_merge_config(vdev);
+
+    pdev->reused = false;
+
+    return 0;
+}
+
+static bool vfio_pci_needed(void *opaque)
+{
+    return cpr_mode() == CPR_MODE_RESTART;
+}
+
+static const VMStateDescription vfio_pci_vmstate = {
+    .name = "vfio-pci",
+    .unmigratable = 1,
+    .version_id = 0,
+    .minimum_version_id = 0,
+    .post_load = vfio_pci_post_load,
+    .needed = vfio_pci_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static void vfio_pci_dev_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
@@ -3282,6 +3338,7 @@  static void vfio_pci_dev_class_init(ObjectClass *klass, void *data)
 
     dc->reset = vfio_pci_reset;
     device_class_set_props(dc, vfio_pci_dev_properties);
+    dc->vmsd = &vfio_pci_vmstate;
     dc->desc = "VFIO-based PCI device assignment";
     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
     pdc->realize = vfio_realize;
diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
index 0ef1b5f..63dd0fe 100644
--- a/hw/vfio/trace-events
+++ b/hw/vfio/trace-events
@@ -118,6 +118,7 @@  vfio_region_sparse_mmap_header(const char *name, int index, int nr_areas) "Devic
 vfio_region_sparse_mmap_entry(int i, unsigned long start, unsigned long end) "sparse entry %d [0x%lx - 0x%lx]"
 vfio_get_dev_region(const char *name, int index, uint32_t type, uint32_t subtype) "%s index %d, %08x/%0x8"
 vfio_dma_unmap_overflow_workaround(void) ""
+vfio_region_remap(const char *name, int fd, uint64_t iova_start, uint64_t iova_end, void *vaddr) "%s fd %d 0x%"PRIx64" - 0x%"PRIx64" [%p]"
 
 # platform.c
 vfio_platform_base_device_init(char *name, int groupid) "%s belongs to group #%d"
diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
index bf5be06..f079423 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -360,6 +360,7 @@  struct PCIDevice {
     /* ID of standby device in net_failover pair */
     char *failover_pair_id;
     uint32_t acpi_index;
+    bool reused;
 };
 
 void pci_register_bar(PCIDevice *pci_dev, int region_num,
diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index cb04cc6..0766cc4 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -85,6 +85,7 @@  typedef struct VFIOContainer {
     Error *error;
     bool initialized;
     bool dirty_pages_supported;
+    bool reused;
     uint64_t dirty_pgsizes;
     uint64_t max_dirty_bitmap_size;
     unsigned long pgsizes;
@@ -136,6 +137,7 @@  typedef struct VFIODevice {
     bool no_mmap;
     bool ram_block_discard_allowed;
     bool enable_migration;
+    bool reused;
     VFIODeviceOps *ops;
     unsigned int num_irqs;
     unsigned int num_regions;
@@ -212,6 +214,9 @@  VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp);
 void vfio_put_group(VFIOGroup *group);
 int vfio_get_device(VFIOGroup *group, const char *name,
                     VFIODevice *vbasedev, Error **errp);
+int vfio_cpr_save(Error **errp);
+int vfio_cpr_load(Error **errp);
+bool vfio_is_cpr_capable(VFIOContainer *container, Error **errp);
 
 extern const MemoryRegionOps vfio_region_ops;
 typedef QLIST_HEAD(VFIOGroupList, VFIOGroup) VFIOGroupList;
diff --git a/include/migration/cpr.h b/include/migration/cpr.h
index 83f69c9..e9b987f 100644
--- a/include/migration/cpr.h
+++ b/include/migration/cpr.h
@@ -25,4 +25,7 @@  int cpr_state_load(Error **errp);
 CprMode cpr_state_mode(void);
 void cpr_state_print(void);
 
+int cpr_vfio_save(Error **errp);
+int cpr_vfio_load(Error **errp);
+
 #endif
diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h
index e680594..48a02c0 100644
--- a/linux-headers/linux/vfio.h
+++ b/linux-headers/linux/vfio.h
@@ -52,6 +52,12 @@ 
 /* Supports the vaddr flag for DMA map and unmap */
 #define VFIO_UPDATE_VADDR		10
 
+/* Supports VFIO_DMA_UNMAP_FLAG_ALL */
+#define VFIO_UNMAP_ALL                        9
+
+/* Supports VFIO DMA map and unmap with the VADDR flag */
+#define VFIO_UPDATE_VADDR              10
+
 /*
  * The IOCTL interface is designed for extensibility by embedding the
  * structure length (argsz) and flags into structures passed between
diff --git a/migration/cpr.c b/migration/cpr.c
index 72a5f4b..16f11bd 100644
--- a/migration/cpr.c
+++ b/migration/cpr.c
@@ -7,6 +7,7 @@ 
 
 #include "qemu/osdep.h"
 #include "exec/memory.h"
+#include "hw/vfio/vfio-common.h"
 #include "io/channel-buffer.h"
 #include "io/channel-file.h"
 #include "migration.h"
@@ -108,7 +109,9 @@  void qmp_cpr_exec(strList *args, Error **errp)
         error_setg(errp, "cpr-exec requires cpr-save with restart mode");
         return;
     }
-
+    if (cpr_vfio_save(errp)) {
+        return;
+    }
     cpr_walk_fd(preserve_fd, 0);
     if (cpr_state_save(errp)) {
         return;
@@ -148,6 +151,11 @@  void qmp_cpr_load(const char *filename, Error **errp)
         goto out;
     }
 
+    if (cpr_active_mode == CPR_MODE_RESTART &&
+        cpr_vfio_load(errp)) {
+        goto out;
+    }
+
     state = global_state_get_runstate();
     if (state == RUN_STATE_RUNNING) {
         vm_start();
diff --git a/migration/target.c b/migration/target.c
index 4390bf0..984bc9e 100644
--- a/migration/target.c
+++ b/migration/target.c
@@ -8,6 +8,7 @@ 
 #include "qemu/osdep.h"
 #include "qapi/qapi-types-migration.h"
 #include "migration.h"
+#include "migration/cpr.h"
 #include CONFIG_DEVICES
 
 #ifdef CONFIG_VFIO
@@ -22,8 +23,21 @@  void populate_vfio_info(MigrationInfo *info)
         info->vfio->transferred = vfio_mig_bytes_transferred();
     }
 }
+
+int cpr_vfio_save(Error **errp)
+{
+    return vfio_cpr_save(errp);
+}
+
+int cpr_vfio_load(Error **errp)
+{
+    return vfio_cpr_load(errp);
+}
+
 #else
 
 void populate_vfio_info(MigrationInfo *info) {}
+int cpr_vfio_save(Error **errp) { return 0; }
+int cpr_vfio_load(Error **errp) { return 0; }
 
 #endif /* CONFIG_VFIO */